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ACS Macro Lett 2022 May 18:733-738. Epub 2022 May 18.

Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.

Despite recent advances in polymer mechanochemistry, a more complete understanding of the factors that dictate the ultrasound-induced mechanochemical activation efficiency of mechanophores is necessary. Here, we examine how the identity of a mechanophore, and hence its unique force-coupled reactivity, affects the competition between mechanophore activation and nonspecific polymer backbone scission. Polymers incorporating distinct mechanophores but with putatively similar "chain-centeredness" exhibit widely different mechanochemical activation efficiencies. Read More

ACS Macro Lett 2022 May 19:747-752. Epub 2022 May 19.

Department of Macromolecular Science and Engineering, Kyoto Institute of Technology, Sakyo-ku, Kyoto 606-8585, Japan.

-1,4-Polyisoprene (IR) elastomers harden via strain-induced crystallization (SIC) when the imposed stretch (λ) exceeds the onset value of SIC (λ*). We investigate the Mode-I fast crack growth in the IR sheets as a function of λ in a pure shear geometry. The steady-state crack velocity () increases with increasing λ, and exceeds the shear wave speed of sound at λ > λ. Read More

ACS Macro Lett 2016 Apr 11;5(4):547-551. Epub 2016 Apr 11.

The State Key Laboratory of Molecular Engineering of Polymers, Collaborative Innovation Center of Polymers and Polymer Composite Materials, Department of Macromolecular Science, Fudan University, Shanghai, 200433, China.

In this report, we synthesized layered amphiphilic dendrimer-like block copolymers containing a polystyrene core and poly(--butoxystyrene)/poly(-hydroxylstyrene) shell (coded G4-PBOS/G4-PHOS). The synthetic method is easy involving anionic polymerization, epoxidation, ring-opening reaction and hydrolysis reaction. The hydrolyzed G4-PBOS was soluble in alkaline water and behaved as unimolecular micelle, as demonstrated by the results of DLS, cryo- and normal TEM, and pyrene entrapping experiment. Read More

ACS Macro Lett 2016 Apr 15;5(4):439-443. Epub 2016 Mar 15.

Department of Materials Science and Engineering, Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States.

We show evidence of thickness-dependent elastic mechanical moduli that are associated largely with the effects of architecture (topology) and the overall shape of the macromolecule. Atomic force microscopy (AFM) based nanoindentation experiments were performed on linear chain polystyrene (LPS) and star-shaped polystyrene (SPS) macromolecules of varying functionalities (number of arms, ) and molecular weights per arm . The out-of-plane elastic moduli () increased with decreasing film thickness, , for less than a threshold film thickness, . Read More

ACS Macro Lett 2016 Apr 5;5(4):515-518. Epub 2016 Apr 5.

Departments of Chemistry and Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States.

Polyurethanes (PUs), in the form of coatings, adhesives, sealants, elastomers, and foams, play a vital role in the consumer goods, automotive, and construction industries. However, the inevitable disposal of nondegradable postconsumer polyurethane products constitutes a massive waste management problem that has yet to be solved. We address this challenge through the synthesis of biobased and chemically recyclable polyurethanes. Read More

ACS Macro Lett 2016 Apr 21;5(4):460-465. Epub 2016 Mar 21.

Department of Chemistry and McKetta Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States.

Block copolymers are potentially useful materials for large-area 2-D patterning applications due to their spontaneous self-assembly into sub-50 nm domains. However, most thin film engineering applications require patterns of prescribed size, shape, and organization. Photopatterning is a logical choice for manipulating block copolymer features since advanced lithography tools can pattern areas as small as a single block copolymer domain. Read More

ACS Macro Lett 2016 Apr 9;5(4):424-429. Epub 2016 Mar 9.

The Dow Chemical Company, Freeport, Texas 77541 United States.

Thermoplastic polyhydroxyurethanes (PHUs) were synthesized from cyclic carbonate aminolysis. Because of the hydroxyl groups in PHU, the choice of soft segment has a dramatic influence on nanophase separation in polyether-based PHUs. Use of a polyethylene glycol-based soft segment, which results in nanophase-separated thermoplastic polyurethane elastomers (TPUs), leads to single-phase PHUs that flow under the force of gravity. Read More

ACS Macro Lett 2016 Apr 17;5(4):444-449. Epub 2016 Mar 17.

Centre for Advanced Macromolecular Design (CAMD) and Australian Centre for NanoMedicine (ACN), School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052, Australia.

Well-defined poly(ε-caprolactone)--poly(methyl acrylate) (PCL--PMA) block copolymers were synthesized at ambient temperature by one-pot combination of diphenyl phosphate (DPP)-catalyzed ring-opening polymerization (ROP) and photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. Full orthogonality of PET-RAFT polymerization and DPP-catalyzed ROP was confirmed by kinetic studies, which allowed facile synthesis of PCL--PMA block copolymers without a specific polymerization sequence. The resulting PCL--PMA block copolymers synthesized by either sequential or simultaneous ROP and PET-RAFT polymerization showed remarkably low molecular weight distributions (≤1. Read More

ACS Macro Lett 2016 Apr 23;5(4):466-470. Epub 2016 Mar 23.

The George and Josephine Butler Laboratory for Polymer Research, Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, United States.

A kinetic study revealed that the acid-catalyzed (-TSA) equilibration of MeSi(OMe) and MeSi(OEt), forming MeSi(OEt)OMe, is established in 300 min in benzene at room temperature. This silicon acetal metathesis reaction is exploited for the step-growth polymerization of bis-silicon acetals (MeOSiMeOROSiMeOMe) with metathetical loss of MeSi(OMe). Thus, a convenient and generalized silicon acetal metathesis polymerization (SAMP) method is introduced as the acid-catalyzed copolymerization of a diol (HOROH) and MeSi(OMe), driven by elimination of methanol and/or MeSi(OMe). Read More

ACS Macro Lett 2016 Apr 30;5(4):487-492. Epub 2016 Mar 30.

Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.

Polyelectrolyte microcapsules represent a versatile platform to encapsulate and release active ingredients. Understanding the effect of environmental conditions on the mechanical properties of microcapsules is critically important for enabling their applications under various settings. In this report, we investigate the effect of solution pH on the mechanical properties of polyelectrolyte microcapsules made of two weak polyelectrolytes (poly(acrylic acid) and branched poly(ethylenimine)), formed via recently introduced nanoscale interfacial complexation in emulsion (NICE). Read More

ACS Macro Lett 2016 Apr 9;5(4):430-434. Epub 2016 Mar 9.

Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, United Kingdom.

We study the conformations of polymer chains in polymer-graphene oxide nanocomposites. We show that the chains have a reduced radius of gyration that is consistent with confinement at a solid interface in the melt, as is expected for well-dispersed, high aspect ratio nanoparticles that are much larger than the polymer coil size. We show that confinement of the polymer chains causes a corresponding reduction in interchain entanglements, and we calculate a contribution to the plateau modulus from the distorted polymer network via a simple scaling argument. Read More

ACS Macro Lett 2016 Apr 18;5(4):455-459. Epub 2016 Mar 18.

Molecular Foundry, Lawrence Berkeley National Lab, Berkeley, California 94720, United States.

Conductive polymers such as PEDOT:PSS hold great promise as flexible thermoelectric devices. The thermoelectric power factor of PEDOT:PSS is small relative to inorganic materials because the Seebeck coefficient is small. Ion conducting materials have previously been demonstrated to have very large Seebeck coefficients, and a major advantage of polymers over inorganics is the high room temperature ionic conductivity. Read More

ACS Macro Lett 2016 Apr 23;5(4):471-475. Epub 2016 Mar 23.

Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.

We report on the conformal coating of thickness-tunable multilayers directly onto the sulfur (S) cathodes by the layer-by-layer (LbL) deposition for the significant improvement in the performances of Li-S batteries even without key additives (LiNO) in the electrolyte. Poly(ethylene oxide) (PEO)/poly(acrylic acid) (PAA) multilayers on a single poly(allylamine hydrochloride) (PAH)/PAA priming bilayer, deposited on the S cathodes, effectively protected from the polysulfide leakage, while providing a Li ion diffusion channel. As a result, PAH/PAA/(PEO/PAA) multilayer-coated cathodes exhibited the highest capacity retention (806 mAh g) after 100 cycles at 0. Read More

ACS Macro Lett 2016 Apr 4;5(4):509-514. Epub 2016 Apr 4.

Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309, United States.

Previous studies of polymer motion at solid/liquid interfaces described the transport in the context of a continuous time random walk (CTRW) process, in which diffusion switches between desorption-mediated "flights" (i.e., hopping) and surface-adsorbed waiting-time intervals. Read More

ACS Macro Lett 2016 Apr 7;5(4):528-532. Epub 2016 Apr 7.

Bundesanstalt für Materialforschung und-prüfung (BAM), Unter den Eichen 87, 12205 Berlin, Germany.

The increasing demand for energy efficient separation processes fosters the development of new high performance polymers as selective separation layers for membranes. PIM-1 is the archetypal representative of the class of polymers of intrinsic microporosity (PIM) which are considered most promising in this sector, especially for gas separations. Since their introduction, PIMs stimulated a vast amount of research in this field and meanwhile evolved to the state-of-the-art in membrane technology for gas separation. Read More

ACS Macro Lett 2016 Apr 1;5(4):504-508. Epub 2016 Apr 1.

Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States.

We report the structural relaxation process of irreversibly adsorbed polymer chains via thermal annealing that lie flat on a solid ("flattened chains"). Amorphous polystyrene and quartz, which together constitute a weakly attractive system, was used as a model where the local chain conformations of the flattened chains were investigated by sum frequency generation spectroscopy (SFG). Two different film preparation processes (i. Read More

ACS Macro Lett 2016 Apr 8;5(4):537-543. Epub 2016 Apr 8.

Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.

The design of solid-state electrolytes for electrochemical applications that utilize polymerized ionic liquids (polyILs) would greatly benefit from a molecular-level understanding of structure-function relationships. We herein use atomistic molecular dynamics simulations to investigate the structural properties of a homologous series of poly(-alkyl-vinylimidzolium bistrifluoromethylsulfonylimide) poly(nVim Tf2N) and present the first direct comparison of the structure factors obtained from X-ray scattering and simulations. Excellent agreement is found in terms of peak position and shape. Read More

ACS Macro Lett 2016 Apr 29;5(4):481-486. Epub 2016 Mar 29.

Department of Mechanical Engineering, Department of Civil & Environmental Engineering, and Department of Materials Science & Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3109, United States.

Despite having very similar bulk properties such as glass-transition temperature (), density, and fragility, polystyrene (PS) and poly(methyl methacrylate) (PMMA) exhibit characteristically different depression in free-standing ultrathin films due to free surface effects. Here we explain this difference using our recently established chemistry-specific coarse-grained (CG) models for these two polymers. Models capture the dissimilar scaling of with free-standing film thickness as seen in experiments and enable us to quantify the size of the regions near free surfaces over which chain relaxation exhibits differences from bulk. Read More

ACS Macro Lett 2016 Apr 30;5(4):498-503. Epub 2016 Mar 30.

Preparative Macromolecular Chemistry, Institut für Technische Chemie und Polymerchemie, Karlsruhe Institute of Technology (KIT), Engesserstr. 18, 76131 Karlsruhe, Germany.

Single molecule force spectroscopy (SMFS) is employed to gain insight into reversible addition-fragmentation chain transfer (RAFT) polymerization processes with living characteristics on glass surfaces. Surface-initiated (SI)-RAFT was selected to grow poly(hydroxyethyl methacrylate) (PHEMA). After aminolysis of the RAFT chain termini, thiol moieties serve as anchoring points for the gold tip of an atomic force microscope. Read More

ACS Macro Lett 2016 Apr 24;5(4):476-480. Epub 2016 Mar 24.

Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.

Dielectric relaxation spectroscopy is employed to investigate charge transport properties of two polyester ether ionomers in the bulk state and when confined in unidirectional nanoporous membranes (average pore diameter = 7.5 nm). Under nanometric confinement in nonsilanized pores, the macroscopic transport quantities (dc conductivity and characteristic frequency rate) are lower by about 1. Read More

ACS Macro Lett 2016 Apr 7;5(4):523-527. Epub 2016 Apr 7.

Department of Chemical Engineering, Columbia University, New York, New York 10027, United States.

Chain behavior has been determined in polymer nanocomposites (PNCs) comprised of well-dispersed 12 nm diameter silica nanoparticles (NPs) in poly(methyl methacrylate) (PMMA) matrices by Small-Angle Neutron Scattering (SANS) measurements under the Zero Average Contrast (ZAC) condition. In particular, we directly characterize the bound polymer layer surrounding the NPs, revealing the bound layer profile. The SANS spectra in the high- region also show no significant change in the bulk polymer radius of gyration on the addition of the NPs. Read More

ACS Macro Lett 2016 Apr 17;5(4):450-454. Epub 2016 Mar 17.

Ministry of Education Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources, School of Chemistry and Pharmaceutical Science, Guangxi Normal University, Guilin 541004, P. R. China.

A novel multifunctional aggregation-induced emission (AIE) nanoaggregate for targeted imaging and enzyme-triggered chemotherapy was successfully fabricated via a one-step assembly. In this system, a quaternary ammonium-modified tetraphenylethene derivative (QA-TPE) acted as the AIE fluorophore as well as the chemotherapeutic agent, and a water-soluble acidic polysaccharide, hyaluronic acid (HA) acted as the aggregation-inducing scaffold, AIE turn-on agent, and targeting agent for CD44 receptor-mediated cancer cells. More importantly, HA endowed the QA-TPE/HA nanoaggregate both good biocompatibility and hysteretic chemotherapy activity, which were achieved by controlling the release of QA-TPE using the endogenous HAase in CD44 receptor-mediated cancer cells. Read More

ACS Macro Lett 2016 Apr 10;5(4):435-438. Epub 2016 Mar 10.

Shanghai Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, East China Normal University, North Zhongshan Road 3663, Shanghai 200062, China.

Homogeneous catalysts generally show higher catalytic activities, while heterogeneous catalysts are more easily separated from products. To combine the advantages of heterogeneous and homogeneous catalysts has been of great interest for many years. Here, we report a kind of facilely prepared cross-linked poly(ionic liquid)s (PILs) with swelling property to increase catalytic activities of heterogeneous catalysts. Read More

ACS Macro Lett 2016 Apr 8;5(4):533-536. Epub 2016 Apr 8.

Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120, United States.

In the search for new synthetic routes toward greener and more facile syntheses of conjugated polymers, C-H functionalization provides a promising solution by minimizing the production and processing of aryl halide monomer precursors used in traditional organometallic coupling reactions. In this paper, we investigate the use of Au(I) and its ability to directly C-H activate 2-bromo-3-hexylthiophene to form a reactive monomer species, bypassing the typical Grignard monomer formation from a dihalogenated thiophene. Addition of Pd-PEPPSI-iPr as a palladium catalyst source in the presence of the resultant aurylated thiophene monomer yielded poly(3-hexylthiophene) as observed by both NMR and GPC. Read More

ACS Macro Lett 2016 Apr 8;5(4):544-546. Epub 2016 Apr 8.

IBM Corporation, Tucson, Arizona 85744, United States.

A new polyacrylate, poly(methylidenelactide), with high thermal stability and derived from biobased resources is reported. This polymer is formed from the radical polymerization of a modified lactide derivative and represents one of the few examples of an acrylic from which the entire mass is bioderived and is made from a simplistic synthesis. Furthermore, poly(methylidenelactide) serves as a foundation for a platform of new acrylic structures, owing to pendant cyclic diesters that are susceptible to postpolymerization modification via simple transesterification chemistry. Read More

ACS Macro Lett 2016 Apr 5;5(4):519-522. Epub 2016 Apr 5.

Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-8501, Japan.

Random poly(quinoxaline-2,3-diyl) copolymers, containing chiral ()-3-octyloxymethyl and achiral propoxymethyl side chain units, experience an abnormal sergeants-and-soldiers effect, that is, they adopt, depending on the chiral monomer mole fraction, either - or -helical conformations in anisole (PhOCH) and benzotrifluoride (PhCF). In benzene (PhH) and toluene (PhCH), these copolymers exclusively adopt an -helical conformation, regardless of the chiral monomer mole fraction. For a co-300mer, with a 40% mole fraction of chiral units, the selective induction of an -helix (>99%) was observed in PhH, while in PhCF, a -helical conformation was induced selectively (>99%). Read More

ACS Macro Lett 2016 Apr 30;5(4):493-497. Epub 2016 Mar 30.

Center for Polymer-based Protein Engineering, ICES, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.

While most effective in aqueous environments, enzymes are also able to catalyze reactions in essentially anhydrous organic media. Enzyme activity in organic solvents is limited as a result of inefficient substrate binding, lack of solubility, and inactivation by hydrophilic anhydrous solvents. With these facts in mind, atom transfer radical polymerization was used to synthesize chymotrypsin-poly(2-(dimethylamino)ethyl methacrylate) (CT-pDMAEMA) conjugates designed to be soluble and active in acetonitrile. Read More

ACS Macro Lett 2016 Aug 15;5(8):904-908. Epub 2016 Jul 15.

Department of Chemistry, Centre for Self-Assembled Chemical Structures, and Pulp and Paper Research Centre, McGill University, Montreal, 3420 University Street, QC H3A 2A7, Canada.

Trapping nanosized drugs in ultrasoft, shear-thinning hydrogels with large pores is of particular interest, yet a persistent challenge in nanomedicine due to the lack of hydrodynamic confinement. Engineering molecular interactions between a macromolecule and a supramolecular gel may address this shortcoming, providing a key route to develop advanced drug carriers without compromising matrix elasticity. Here, we show that ultrasoft zirconium-based metallogels are able to trap and reconfigure model nanodrugs (e. Read More

ACS Macro Lett 2016 Aug 13;5(8):900-903. Epub 2016 Jul 13.

College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Chengdu 610065, China.

We study the influence of particle shape on shear-induced droplet deformation in polymeric emulsions. During shearing, droplets become elongated and rotate periodically about their major axes while aligning along the vorticity direction in ellipsoid-filled emulsions, while similar behavior is not observed in the pristine, microsphere-filled or ellipsoid-filled inverse systems. Based on the Jeffery orbit theory, the formation of anisotropic droplets with extremely small Reynolds number due to arrested coalescence in Newtonian matrix and strong confinement effect are suggested to be responsible for the vorticity alignment of droplets during slow shearing. Read More

ACS Macro Lett 2016 Aug 11;5(8):894-899. Epub 2016 Jul 11.

Department of Polymeric Materials and Engineering, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China.

We report a fast alcoholic photoinitiated polymerization-induced self-assembly (photo-PISA) formulation via photoinitiated RAFT dispersion polymerization of isobornyl acrylate (IBOA) in an ethanol/water mixture at 40 °C using a monomethoxy poly(ethylene glycol) (mPEG) based chain transfer agent. Polymerization proceeded rapidly via the exposure to visible light irradiation (405 nm, 0.5 mW/cm), and high monomer conversion (>95%) was achieved within 30 min. Read More