Publications by authors named "Dean C Webster"

24 Publications

  • Page 1 of 1

Studying the Effect of Pre-Polymer Composition and Incorporation of Surface-Modifying Amphiphilic Additives on the Fouling-Release Performance of Amphiphilic Siloxane-Polyurethane Coatings.

ACS Appl Mater Interfaces 2022 Aug 8. Epub 2022 Aug 8.

Department of Coatings and Polymeric, North Dakota State University, Fargo, North Dakota 58108, United States.

Combining amphiphilic fouling-release (FR) coatings with the surface-active nature of amphiphilic additives can improve the antifouling/fouling-release (AF/FR) properties needed to offer broad-spectrum resistance to marine biofoulants. This work is focused on further tuning the amphiphilic character of a previously developed amphiphilic siloxane-polyurethane (SiPU) coating by varying the amount of PDMS and PEG in the base system. Furthermore, surface-modifying amphiphilic additives (SMAAs) were incorporated into these amphiphilic FR SiPU coatings in varying amounts. ATR-FTIR, contact angle and surface energy measurements, and AFM were performed to assess changes in surface composition, wettability, and morphology. AF/FR properties were evaluated using laboratory biological assays involving , , , , and . The surfaces of these coatings varied significantly upon changes in PDMS and PEG content in the coating matrix, as well as with changes in SMAA incorporation. AF/FR properties were also significantly changed, with formulations containing the highest amounts of SMAA showing very high removal properties compared to other experimental formulations, in some cases better than that of commercial standard FR coatings.
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http://dx.doi.org/10.1021/acsami.2c10983DOI Listing
August 2022

Grooming of fouling-release coatings to control marine fouling and determining how grooming affects the surface.

Biofouling 2022 04 2;38(4):384-400. Epub 2022 Jun 2.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota, USA.

Grooming may be an effective technique to control marine biofouling without damaging the coating or discharging active ingredients into the environment. This study assessed the grooming performance of three experimental biocide-free siloxane polyurethane (SiPU) fouling-release coatings. Coatings were statically immersed in Port Canaveral, Florida, and groomed every two weeks for five months using three different brush types. The ungroomed panels became heavily fouled with biofilm, tubeworms, barnacles, and bryozoans. Two of the brushes were able to control the fouling with a coverage of <5%. The commercial silicone elastomer coating was damaged from grooming procedures, while the SiPU coatings were not. Laboratory biological assays were carried out and mirrored the grooming results. Through surface characterization techniques, it was concluded that the coatings were unaffected by the grooming procedures. This study shows that marine fouling on durable SiPU fouling-release coatings can be controlled grooming without damage or changing the surface properties.
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http://dx.doi.org/10.1080/08927014.2022.2084389DOI Listing
April 2022

Towards Upcycling Biomass-Derived Crosslinked Polymers with Light.

Angew Chem Int Ed Engl 2022 08 31;61(31):e202203353. Epub 2022 May 31.

Center for Photochemical Science and Department of Chemistry, Bowling Green State University, Bowling Green, OH 43403, USA.

Photodegradable, recyclable, and renewable, crosslinked polymers from bioresources show promise towards developing a sustainable strategy to address the issue of plastics degradability and recyclability. Photo processes are not widely exploited for upcycling polymers in spite of the potential to have spatial and temporal control of the degradation in addition to being a green process. In this report we highlight a methodology in which biomass-derived crosslinked polymers can be programmed to degrade at ≈300 nm with ≈60 % recovery of the monomer. The recovered monomer was recycled back to the crosslinked polymer.
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http://dx.doi.org/10.1002/anie.202203353DOI Listing
August 2022

Durable siloxane-polyurethane coatings for mitigating freshwater mussel fouling.

Biofouling 2022 03 25;38(3):260-270. Epub 2022 Mar 25.

Department of Coatings & Polymeric Materials, North Dakota State University, Fargo, North Dakota, USA.

Siloxane-polyurethane hybrid coatings were assessed for biofouling control caused by freshwater mussels. Invasive species such as zebra () and quagga () mussels have rapidly spread through the waterways in the United States causing major concerns in reservoir infrastructure and freshwater lakes. Current coating solutions such as biocidal anti-fouling coatings are not suitable given the released biocides which may accumulate in reservoirs. Biocide free fouling release coatings based on silicone elastomers do not have adequate mechanical durability. The siloxane-polyurethane (SiPU) coatings were evaluated using model organism laboratory assays and real-life performance was evaluated in the freshwater field environment. Two coating compositions displayed excellent performance in field trials for up to 2+ years. The surface analysis experiments of the coatings indicate that the morphology of the coatings is affected by the formulations' solvent choice. These coatings show great promise in mitigating biofouling predominated by freshwater mussels.
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http://dx.doi.org/10.1080/08927014.2022.2056033DOI Listing
March 2022

Surface modifying amphiphilic additives and their effect on the fouling-release performance of siloxane-polyurethane coatings.

Biofouling 2021 03 24;37(3):309-326. Epub 2021 Mar 24.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND, USA.

In this work, surface-modifying amphiphilic additives (SMAAs) were synthesized hydrosilylation using various polymethylhydrosiloxanes (PMHS) and allyl-terminated polyethylene glycol monomethyl ethers (APEG) of varying molecular weights. The additives synthesized were incorporated into a hydrophobic, self-stratifying siloxane-polyurethane (SiPU) coating system to produce an amphiphilic surface. Contact angle experiments and atomic force microscopy (AFM), in a dry and hydrated state, were performed to assess changes in surface wettability and morphology. The antifouling and fouling-release (AF/FR) performances were evaluated by performing laboratory biological assays using the marine bacterium , the microalga , the macroalga , the barnacle , and the marine mussel, . Several of the formulations showed improved AF/FR performance the base SiPU and performed better than some of the commercial standard marine coatings. Formulations containing SMAAs with a low grafting density of relatively high molecular weight PEG chains showed the best performance overall.
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http://dx.doi.org/10.1080/08927014.2021.1901891DOI Listing
March 2021

Critical Amphiphilic Concentration: Effect of the Extent of Amphiphilicity on Marine Fouling-Release Performance.

Langmuir 2021 03 14;37(8):2728-2739. Epub 2021 Feb 14.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States.

Amphiphilic surfaces, containing both hydrophilic and hydrophobic domains, offer desirable performance for many applications such as marine coatings or anti-icing purposes. This work explores the effect of the concentration of amphiphilic moieties on converting a polyurethane (PU) system to a coating having fouling-release properties. A novel amphiphilic compound is synthesized and added at increasing amounts to a PU system, where the amount of the additive is the only variable in the study. The additive-modified surfaces are characterized by a variety of techniques including ATR-FTIR, XPS, contact angle measurements, and AFM. Surface characterizations indicate the presence of amphiphilic domains on the surface due to the introduction of the self-stratifying amphiphilic additive. The fouling-release properties of the surfaces are assessed with three biological assays using , , and as the test organisms. A change in the fouling-release performance is observed and plateaued once a certain amount of amphiphilicity is attained in the coating system, which we call the (CAC).
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http://dx.doi.org/10.1021/acs.langmuir.0c03446DOI Listing
March 2021

A Preliminary Environmental Assessment of Epoxidized Sucrose Soyate (ESS)-Based Biocomposite.

Molecules 2020 Jun 17;25(12). Epub 2020 Jun 17.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND 58108, USA.

Biocomposites can be both environmentally and economically beneficial: during their life cycle they generally use and generate less petroleum-based carbon, and when produced from the byproduct of another industry or recycled back to the manufacturing process, they will bring additional economic benefits through contributing to a circular economy. Here we investigate and compare the environmental performance of a biocomposite composed of a soybean oil-based resin (epoxidized sucrose soyate) and flax-based reinforcement using life cycle assessment (LCA) methodology. We evaluate the main environmental impacts that are generated during the production of the bio-based resin used in the biocomposite, as well as the biocomposite itself. We compare the life cycle impacts of the proposed biocomposite to a functionally similar petroleum-based resin and flax fiber reinforced composite, to identify tradeoffs between the environmental performance of the two products. We demonstrate that the bio-based resin (epoxidized sucrose soyate) compared to a conventional (bisphenol A-based) resin shows lower negative environmental impacts in most studied categories. When comparing the biocomposite to the fossil fuel derived composite, it is demonstrated that using epoxidized sucrose soyate versus a bisphenol A (BPA)-based epoxy resin can improve the environmental performance of the composite in most categories except eutrophication and ozone layer depletion. For future designs, considering an alternative cross-linker to facilitate the bond between the bio-based resin and the flax fiber, may help improve the overall environmental performance of the biocomposite. An uncertainty analysis was also performed to evaluate the effect of variation in LCA model inputs on the environmental results for both the biocomposite and composite. The findings show a better overall carbon footprint for the biocomposite compared to the BPA-based composite at almost all times, demonstrating a good potential for marketability especially in the presence of incentives or regulations that address reducing the carbon intensity of products. This analysis allowed us to pinpoint hotspots in the biocomposite's supply chain and recommend future modifications to improve the product's sustainability.
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http://dx.doi.org/10.3390/molecules25122797DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7356212PMC
June 2020

Soysome: A Surfactant-Free, Fully Biobased, Self-Assembled Platform for Nanoscale Drug Delivery Applications.

ACS Appl Bio Mater 2018 Dec 4;1(6):1830-1841. Epub 2018 Dec 4.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, United States.

A new class of biobased nanocarriers, soysomes, has been discovered and investigated. These nanocarriers are derived from a synthetically accessible, scalable macromolecule, methoxylated sucrose soyate polyol (MSSP), derived from chemical building blocks obtained from soybean oil and sucrose. We observed for the first time that MSSP, when dissolved in an organic solvent of different polarity and slowly added to an aqueous phase at a predetermined rate under "nanoprecipitation" conditions, will form a stable, self-assembled structure with a size range from 100 to 200 nm depending on the polarity difference between the precipitating solvent pairs. Without the aid of poly(ethylene glycol) or any surfactants, these soysomes were found to be stable in water for an extended period and can withstand the destabilizing effect of time, temperature, and pH. We also found that the soysomes were able to encapsulate and release a hydrophobic bioactive compound, such as curcumin. Both MSSP and their self-assembled structures were highly biocompatible and did not trigger cellular toxicity to mammalian cell lines. Our experiments showed that such 100% biobased, noncytotoxic material as MSSP and a related class of products have the potential for use toward the sustainable manufacturing of drug nanocarriers for biomedical applications.
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http://dx.doi.org/10.1021/acsabm.8b00317DOI Listing
December 2018

Fouling-Release Performance of Silicone Oil-Modified Siloxane-Polyurethane Coatings.

ACS Appl Mater Interfaces 2016 Oct 11;8(42):29025-29036. Epub 2016 Oct 11.

Department of Coatings and Polymeric Materials, North Dakota State University , Fargo North Dakota 58108, United States.

The effect of incorporation of silicone oils into a siloxane-polyurethane fouling-release coatings system was explored. Incorporation of phenylmethyl silicone oil has been shown to improve the fouling-release performance of silicone-based fouling-release coatings through increased interfacial slippage. The extent of improvement is highly dependent upon the type and composition of silicone oil used. The siloxane-polyurethane (SiPU) coating system is a tough fouling-release solution, which combines the mechanical durability of polyurethane while maintaining comparable fouling-release performance with regard to commercial standards. To further improve the fouling-release performance of the siloxane-PU coating system, the use of phenylmethyl silicones oils was studied. Coatings formulations were prepared incorporating phenylmethyl silicone oils having a range of compositions and viscosities. Contact angle and surface energy measurements were conducted to evaluate the surface wettability of the coatings. X-ray photoelectron spectroscopy (XPS) depth profiling experiments demonstrated self-stratification of silicone oil along with siloxane to the coating-air interface. Several coating formulations displayed improved or comparable fouling-release performance to commercial standards during laboratory biological assay tests for microalgae (Navicula incerta), macroalgae (Ulva linza), adult barnacles (Balanus amphitrite syn. Amphibalanus amphitrite), and mussels (Geukensia demissa). Selected silicone-oil-modified siloxane-PU coatings also demonstrated comparable fouling-release performance in field immersion trials. In general, modifying the siloxane-PU fouling-release coatings with a small amount (1-5 wt % basis) of phenylmethyl silicone oil resulted in improved performance in several laboratory biological assays and in long-term field immersion assessments.
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http://dx.doi.org/10.1021/acsami.6b09484DOI Listing
October 2016

Comparison of laboratory and field testing performance evaluations of siloxane-polyurethane fouling-release marine coatings.

Biofouling 2016 Sep;32(8):949-68

f National University of Singapore, Tropical Marine Science Institute , Singapore.

A series of eight novel siloxane-polyurethane fouling-release (FR) coatings were assessed for their FR performance in both the laboratory and in the field. Laboratory analysis included adhesion assessments of bacteria, microalgae, macroalgal spores, adult barnacles and pseudobarnacles using high-throughput screening techniques, while field evaluations were conducted in accordance with standardized testing methods at three different ocean testing sites over the course of six-months exposure. The data collected were subjected to statistical analysis in order to identify potential correlations. In general, there was good agreement between the laboratory screening assays and the field assessments, with both regimes clearly distinguishing the siloxane-polyurethane compositions comprising monofunctional poly(dimethyl siloxane) (PDMS) (m-PDMS) as possessing superior, broad-spectrum FR properties compared to those prepared with difunctional PDMS (d-PDMS). Of the seven laboratory screening techniques, the Cellulophaga lytica biofilm retraction and reattached barnacle (Amphibalanus amphitrite) adhesion assays were shown to be the most predictive of broad-spectrum field performance.
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http://dx.doi.org/10.1080/08927014.2016.1211269DOI Listing
September 2016

Programmed photodegradation of polymeric/oligomeric materials derived from renewable bioresources.

Angew Chem Int Ed Engl 2015 Jan 12;54(4):1159-63. Epub 2014 Nov 12.

Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND 58108-6050 (USA).

Renewable polymeric materials derived from biomass with built-in phototriggers were synthesized and evaluated for degradation under irradiation of UV light. Complete decomposition of the polymeric materials was observed with recovery of the monomer that was used to resynthesize the polymers.
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http://dx.doi.org/10.1002/anie.201408492DOI Listing
January 2015

Thermoset coatings from epoxidized sucrose soyate and blocked, bio-based dicarboxylic acids.

ChemSusChem 2014 Aug 28;7(8):2289-94. Epub 2014 Apr 28.

Department of Coatings and Polymeric Materials, North Dakota State University, PO Box 6050, Dept 2760, Fargo, ND 58108 (USA).

A new 100% bio-based thermosetting coating system was developed from epoxidized sucrose soyate crosslinked with blocked bio-based dicarboxylic acids. A solvent-free, green method was used to block the carboxylic acid groups and render the acids miscible with the epoxy resin. The thermal reversibility of this blocking allowed for the formulation of epoxy-acid thermoset coatings that are 100% bio-based. This was possible due to the volatility of the vinyl ethers under curing conditions. These systems have good adhesion to metal substrates and perform well under chemical and physical stress. Additionally, the hardness of the coating system is dependent on the chain length of the diacid used, making it tunable.
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http://dx.doi.org/10.1002/cssc.201402091DOI Listing
August 2014

New biobased high functionality polyols and their use in polyurethane coatings.

ChemSusChem 2012 Feb 23;5(2):419-29. Epub 2012 Jan 23.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND 58108, USA.

High-functionality polyols for application in polyurethanes (PUs) were prepared by epoxide ring-opening reactions from epoxidized sucrose esters of soybean oil-epoxidized sucrose soyates-in which secondary hydroxyl groups were generated from epoxides on fatty acid chains. Ester polyols were prepared by using a base-catalyzed acid-epoxy reaction with carboxylic acids (e.g., acetic acid); ether polyols were prepared by using an acid-catalyzed alcohol-epoxy reaction with monoalcohols (e.g., methanol). The polyols were characterized by using gel permeation chromatography, FTIR spectroscopy, (1)H NMR spectroscopy, differential scanning calorimetry (DSC), and viscosity measurements. PU thermosets were prepared by using aliphatic polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate. The properties of the PUs were studied by performing tensile testing, dynamic mechanical analysis, DSC, and thermogravimetric analysis. The properties of PU coatings on steel substrates were evaluated by using ASTM methods to determine coating hardness, adhesion, solvent resistance, and ductility. Compared to a soy triglyceride polyol, sucrose soyate polyols provide greater hardness and range of cross-link density to PU thermosets because of the unique structure of these macromolecules: well-defined compact structures with a rigid sucrose core coupled with high hydroxyl group functionality.
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http://dx.doi.org/10.1002/cssc.201100415DOI Listing
February 2012

Impact of structure and functionality of core polyol in highly functional biobased epoxy resins.

Macromol Rapid Commun 2011 Sep 20;32(17):1324-30. Epub 2011 Jun 20.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58108, USA.

Highly functional biobased epoxy resins were prepared using dipentaerythritol (DPE), tripentaerythritol (TPE), and sucrose as core polyols that were substituted with epoxidized soybean oil fatty acids, and the impact of structure and functionality of the core polyol on the properties of the macromolecular resins and their epoxy-anhydride thermosets was explored. The chemical structures, functional groups, molecular weights, and compositions of epoxies were characterized using nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI MS). The epoxies were also studied for their bulk viscosity, intrinsic viscosity, and density. Crosslinked with dodecenyl succinic anhydride (DDSA), epoxy-anhydride thermosets were evaluated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile tests, and tests of coating properties. Epoxidized soybean oil (ESO) was used as a control. Overall, the sucrose-based thermosets exhibited the highest moduli, having the most rigid and ductile performance while maintaining the highest biobased content. DPE/TPE-based thermosets showed modestly better thermosetting performance than the control ESO thermoset.
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http://dx.doi.org/10.1002/marc.201100215DOI Listing
September 2011

Synthesis of soybean oil-based thiol oligomers.

ChemSusChem 2011 Aug 25;4(8):1135-42. Epub 2011 May 25.

Center for Nanoscale Science and Engineering, 1805 NDSU Research Park Dr., Fargo, ND 58102, USA.

Industrial grade soybean oil (SBO) and thiols were reacted to generate thiol-functionalized oligomers via a thermal, free radical initiated thiol-ene reaction between the SBO double bond moieties and the thiol functional groups. The effect of the reaction conditions, including thiol concentration, catalyst loading level, reaction time, and atmosphere, on the molecular weight and the conversion to the resultant soy-thiols were examined in a combinatorial high-throughput fashion using parallel synthesis, combinatorial FTIR, and rapid gel permeation chromatography (GPC). High thiol functionality and concentration, high thermal free radical catalyst concentration, long reaction time, and the use of a nitrogen reaction atmosphere were found to favor fast consumption of the SBO, and produced high molecular weight products. The thiol conversion during the reaction was inversely affected by a high thiol concentration, but was favored by a long reaction time and an air reaction atmosphere. These experimental observations were explained by the initial low affinity of the SBO and thiol, and the improved affinity between the generated soy-thiol oligomers and unreacted SBO during the reaction. The synthesized soy-thiol oligomers can be used for renewable thiol-ene UV curable materials and high molecular solids and thiourethane thermal cure materials.
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http://dx.doi.org/10.1002/cssc.201100071DOI Listing
August 2011

High biobased content epoxy-anhydride thermosets from epoxidized sucrose esters of Fatty acids.

Biomacromolecules 2011 Jun 24;12(6):2416-28. Epub 2011 May 24.

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, ND, USA.

Novel highly functional biobased epoxy compounds, epoxidized sucrose esters of fatty acids (ESEFAs), were cross-linked with a liquid cycloaliphatic anhydride to prepare polyester thermosets. The degree of cure or conversion was studied using differential scanning calorimetry (DSC), and the sol content of the thermosets was determined using solvent extraction. The mechanical properties were studied using tensile testing to determine Young's modulus, tensile stress, and elongation at break. Dynamic mechanical analysis (DMA) was used to determine glass-transition temperature, storage modulus, and cross-link density. The nanomechanical properties of the surfaces were studied using nanoindentation to determine reduced modulus and indentation hardness. The properties of coatings on steel substrates were studied to determine coating hardness, adhesion, solvent resistance, and mechanical durability. Compared with the control, epoxidized soybean oil, the anhydride-cured ESEFAs have high modulus and are hard and ductile, high-performance thermoset materials while maintaining a high biobased content (71-77% in theory). The exceptional performance of the ESEFAs is attributed to the unique structure of these macromolecules: well-defined compact structures with high epoxide functionality. These biobased thermosets have potential uses in applications such as composites, adhesives, and coatings.
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http://dx.doi.org/10.1021/bm200549cDOI Listing
June 2011

A preliminary study on the properties and fouling-release performance of siloxane-polyurethane coatings prepared from poly(dimethylsiloxane) (PDMS) macromers.

Biofouling 2010 Nov;26(8):961-72

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota, USA.

Siloxane-polyurethane fouling-release (FR) coatings based on aminopropyl terminated poly(dimethylsiloxane) (PDMS) macromers were prepared and characterized for FR performance via laboratory biological assays. These systems rely on self-stratification, resulting in a coating with a siloxane-rich surface and polyurethane bulk. Previously, these coating systems have used PDMS with multiple functional groups which react into the polyurethane bulk. Here, aminopropyl terminated PDMS macromers were prepared, where a single amine group anchors the PDMS in the coating. Coatings were prepared with four molecular weights (1000, 5000, 10,000, and 15,000 g mol⁻¹) and two levels of PDMS (5% and 10%). High water contact angles and low surface energies were observed for the coatings before and after water immersion, along with low pseudobarnacle removal forces. Laboratory bioassays showed reduced biofilm retention of marine bacteria, good removal of diatoms from coatings with low molecular weight PDMS, high removal of algal sporelings (young plants), and low removal forces of live barnacles.
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http://dx.doi.org/10.1080/08927014.2010.531272DOI Listing
November 2010

Automated image-based method for laboratory screening of coating libraries for adhesion of algae and bacterial biofilms.

J Comb Chem 2008 Jul-Aug;10(4):586-94. Epub 2008 Jun 20.

Computer Sciences, Florida Institute of Technology, Melbourne, Florida 32901, USA.

Assessment and down-selection of non-biocidal coatings that prevent the adhesion of fouling organisms in the marine environment requires a hierarchy of laboratory methods to reduce the number of experimental coatings for field testing. Automated image-based methods are described that facilitate rapid, quantitative biological screening of coatings generated through combinatorial polymer chemistry. Algorithms are described that measure the coverage of bacterial and algal biofilms on coatings prepared in 24-well plates and on array panels, respectively. The data are used to calculate adhesion strength of organisms on experimental coatings. The results complement a number of physical and mechanical methods developed to screen large numbers of samples.
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http://dx.doi.org/10.1021/cc800047sDOI Listing
September 2008

Combinatorial materials research applied to the development of new surface coatings VII: an automated system for adhesion testing.

Rev Sci Instrum 2007 Jul;78(7):072213

Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota 58105, USA.

An automated, high-throughput adhesion workflow that enables pseudobarnacle adhesion and coating/substrate adhesion to be measured on coating patches arranged in an array format on 4x8 in.(2) panels was developed. The adhesion workflow consists of the following process steps: (1) application of an adhesive to the coating array; (2) insertion of panels into a clamping device; (3) insertion of aluminum studs into the clamping device and onto coating surfaces, aligned with the adhesive; (4) curing of the adhesive; and (5) automated removal of the aluminum studs. Validation experiments comparing data generated using the automated, high-throughput workflow to data obtained using conventional, manual methods showed that the automated system allows for accurate ranking of relative coating adhesion performance.
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http://dx.doi.org/10.1063/1.2755505DOI Listing
July 2007

Laboratory screening of coating libraries for algal adhesion.

Biofouling 2007 ;23(3-4):267-76

School of Biosciences, The University of Birmingham, UK.

Coatings libraries achieved through a combinatorial chemistry approach, which may generate tens to hundreds of formulations, can be deposited in an array of 12 patches, each approximately 9 cm(2), on 10 x 20 cm primed aluminum panels. However, existing methods to quantify algal biomass on coatings are unsuitable for this type of array format. This paper describes an algorithm modelled on a probability distribution that quantifies the area of surface covered by a green alga from digital images. The method allows coatings with potential fouling-release properties to be down-selected for further evaluation. The use of the algorithm is illustrated by a set of eight siloxane-polyurethane coatings made using organofunctional poly(dimethylsiloxane) (PDMS) and poly(epsilon-caprolactone)-PDMS-poly(epsilon-caprolactone) (PCL-PDMS-PCL) triblock copolymers along with four PDMS standards which were deposited on one panel. Six replicate panels were seeded with Ulva zoospores which grew into sporelings (small plants) that completely covered the surface. The ease of removal of the Ulva sporeling biofilms was determined by automated water jetting at six different impact pressures. The coverage of the biofilm on the twelve individual formulations after jet washing was quantified from the green colour of digital images. The data are discussed in relation to the composition of the coatings.
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http://dx.doi.org/10.1080/08927010701288336DOI Listing
October 2007

Mini-review: combinatorial approaches for the design of novel coating systems.

Biofouling 2007 ;23(3-4):179-92

Department of Coatings and Polymeric Materials, North Dakota State University, Fargo, North Dakota 58105, USA.

Combinatorial and high throughput experimental methods are being applied to the design and development of novel polymers and coatings used in a number of application areas. Methods have been developed for polymer synthesis and screening and for the development of polymer thin film and coating libraries and the screening of these libraries for key properties such as surface energy and modulus. Combinatorial and high throughput methods enable the efficient exploration of a large number of compositional variables over a wide range. In the development of coatings for use in the marine environment, the key challenge is in the development of screening methods that can predict good performance. A number of assays are under development that will permit the rapid screening of the interaction of coatings with representative marine organisms.
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http://dx.doi.org/10.1080/08927010701250948DOI Listing
October 2007

Thermosensitive polymers: synthesis, characterization, and delivery of proteins.

Int J Pharm 2007 Aug 19;341(1-2):68-77. Epub 2007 Apr 19.

Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University Medical Center, Omaha, NE 68178, USA.

Three triblock copolymers based on the poly(lactide) or poly(lactide-co-glycolide) and poly(ethylene glycol) or poly(ethylene oxide) blocks were synthesized and characterized. The weight average molecular weight and number average molecular weight were determined by gel permeation chromatography and proton nuclear magnetic resonance spectroscopy, respectively. Fourier transform infrared spectroscopy was used to determine the completion of synthesis of polymers. Thermoreversible sol-gel transition temperature and concentration were determined by an inverted tube method. Two formulations each of three synthesized polymers containing 5% (w/v) of lysozyme or bromelain but differing in polymer concentrations (20-30%, w/v) were prepared and studied for in vitro release of the incorporated protein. In vitro biocompatibility of the delivery systems was studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell viability assay. Biological activities of lysozyme and bromelain were determined by enzyme activity assays. Critical gelling concentrations were found in the range of 20-30% (w/v). In vitro biocompatibility study showed that all the formulations were biocompatible. Increasing the polymer concentration led to a decrease in burst release and extended the in vitro release of proteins. Furthermore, biological activities of lysozyme and bromelain in released samples were found to be significantly (p<0.05) greater in comparison to the control. Thus, the above thermosensitive polymers were able to deliver proteins in biologically active forms at a controlled rate for 2-8 weeks.
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http://dx.doi.org/10.1016/j.ijpharm.2007.03.054DOI Listing
August 2007

Combinatorial and high-throughput screening of the effect of siloxane composition on the surface properties of crosslinked siloxane-polyurethane coatings.

J Comb Chem 2007 Jan-Feb;9(1):178-88

Department of Coatings and Polymeric Materials, Center for Nanoscale Science and Engineering, North Dakota State University, Fargo, North Dakota 58105, USA.

Libraries of siloxane-polyurethane coatings were designed, formulated, and screened using high-throughput experimentation. Four independent variables that were analyzed were the molecular weight of poly(dimethylsiloxane) (PDMS), presence or absence of poly(epsilon-caprolactone) (PCL) blocks attached to the PDMS backbone, the length of the PCL blocks, and the siloxane polymer level in the coating formulations. In addition to the siloxane libraries (3-aminopropyl-terminated PDMS and poly(epsilon-caprolactone)-poly(dimethylsiloxane)-poly(epsilon-caprolactone) (PCL-PDMS-PCL) triblock copolymers), the coating formulation included a trifunctional isocyanate crosslinker, trifunctional poly(epsilon-caprolactone) polyol, 2,4-pentanedione (pot-life extender), dibutyltin diacetate (catalyst), and a blend of solvents. The resulting coatings were analyzed for their surface energy and pseudobarnacle adhesion both before and after aging the coatings for 30 days in water. The water and methylene iodide contact angle averages increase with increasing molecular weight of PDMS. Coatings prepared from PCL-PDMS-PCL triblock copolymers have lower surface energies than coatings prepared from 3-aminopropyl-terminated PDMS; however, lower pseudobarnacle adhesion results were obtained for the coatings prepared from 3-aminopropyl-terminated PDMS than coatings prepared from PCL-PDMS-PCL triblock copolymers. The siloxane polymer level in the coating formulations does not have a significant effect on the surface energy of the coatings, but it resulted in higher pseudobarnacle adhesion.
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http://dx.doi.org/10.1021/cc060115kDOI Listing
March 2007

Triblock copolymers: synthesis, characterization, and delivery of a model protein.

Int J Pharm 2005 Jan 30;288(2):207-18. Epub 2004 Nov 30.

Department of Pharmaceutical Sciences, North Dakota State University, PO Box 5055, Fargo, ND 58105, USA.

The purpose of this study was to synthesize and characterize biodegradable and thermosensitive triblock copolymers for delivering protein at controlled rate in biologically active form for longer duration of time. A series of thermosensitive triblock copolymers with different block lengths (PLGA-PEG-PLGA) were synthesized by ring-opening polymerization of d,l-lactide and glycolide with polyethylene glycol (PEG) in the presence of stannous octoate. Compositions and molecular weight of triblock copolymers were characterized by 1H NMR spectrometry and gel permeation chromatography, respectively. A single test-tube inverting method was employed to determine the sol-gel transition temperature. Lysozyme was used as a model protein. Lysozyme solution formulation was prepared with different triblock copolymers for in vitro release. Lysozyme concentration and its biological activity in the released sample were determined using a standard MicroBCA method and bacterial cell lysis method, respectively. The effects of varying block lengths and concentrations of copolymers on the in vitro release of lysozyme were evaluated. The release profiles from formulations showed a higher initial release followed by slower release up to 4 weeks. Increasing the block lengths of copolymers decreased burst release of lysozyme from 41.2+/-5.4% to 16.1+/-3.9%. Increasing copolymer concentrations decreased the drug release. Lysozyme in the 4 weeks released samples retained most of its biological activity (>80%). It is feasible to deliver protein in biologically active form for longer duration by varying block lengths and concentrations of triblock copolymers.
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http://dx.doi.org/10.1016/j.ijpharm.2004.09.026DOI Listing
January 2005
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