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A combination of atomic force microscopy-infrared spectroscopy (AFM-IR) and a deuterium-labeled ethylene-propylene (EP) copolymer enables direct nanoscale chemical imaging of all three components in a polyethylene/polypropylene/ethylene-propylene copolymer blend for the first time. AFM-IR is a hybrid technique that provides the spatial resolution of AFM with the chemical selectivity of IR. Deuterium...
Photoinitiators, which can be readily immobilized on surfaces, e.g. on the surface of nanoparticles, have gained considerable attention of both scientists and engineers. The main reason for this interest is that immobilized initiators lead to a covalent linkage between the surface and the resulting polymer chain. Thus, immobilized photoinitiators are expected not to migrate out of the polymer network,...
Molecular dynamic simulations are used to quantify how the mechanical behavior of PPTA crystallites, the fundamental building blocks of aramid fibers such as Kevlar®, depend on strain-rate, temperature, and crystallite size. The (axial) crystallite elastic modulus is found to be independent of strain-rate and decreases with increasing temperature. The crystallite failure strain increases with increasing...
The influence of oleic acid modified Fe3O4 (OA-Fe3O4) nanoparticles on the morphology and foaming behavior of cocontinuous linear low density polyethylene/polystyrene (LLDPE/PS) immiscible blends (60/40 by weight) was studied. The morphology observation showed that the addition of nanofillers resulted in the increased dispersion degree of both LLDPE and PS components and even the transformation of...
Novel materials displaying multi-responsive property were developed by forming crosslinked copolymer systems that exhibit distinct temperature, pH and salt-sensitivity independently. An investigation of the mechanical properties of a novel multi-responsive poly(hydroxypropyl methacrylate) (PHPMA)-based hydrogel system was carried out with two major objectives. First was to study the effect of various...
Spherical poly(acrylic acid)-block-polystyrene (PAA-b-PS) nano-objects were prepared via polymerization induced self-assembly (PISA) and used as templates for the synthesis of silver nanoparticles (Ag NPs). The PAA shells on the spheres acted as templates for the formation of immobilized Ag NPs by loading Ag + ions followed by reduction. The templates covered with discrete Ag NPs showed surface-enhanced...
We demonstrate the reattachment of two chemically-crosslinked poly(ethylene oxide) (PEO) matrix samples prepared with the γ-ray irradiation method by a simple wetting process with a good solvent. The fractured polymer samples can be attached through chain diffusion, interpenetration into a crosslinked network, and intermixing/reentanglement. Reattached samples exhibit similar macro/microstructure...
A new series of functional polyethylene (PE) with ester pendant (−COOR, R = methyl, ethyl, n-propyl, n-butyl, n-octyl, n-dodecyl, n-tetradecyl and n-hexadecyl) on every five main chain carbons were prepared via ring-opening metathesis polymerization (ROMP) of COOR functionalized cyclopentene catalyzed by a ruthenium-based catalyst and subsequent hydrogenation of the ROMP products. High monomer conversions...
A reactive amphiphile, SA1, which comprises a mercaptodecyl oleophilic tail and a β-alanine oleophobic moiety, has been introduced to serve as the building block for supramolecular filler. At least a fraction of SA1 reacts in situ during mechanically mixing and vulcanization with SBR via thiol-ene reaction. Some oxidative dimerization also concomitantly occurs to give DSA1. The chemical coupling between...
Torsional actuation of twisted polymer fibres is the basis for high performance tensile actuation when these fibres are formed into coils. The thermally-induced torsional actuation of twisted polyamide-6 fibres can be predicted by a single helix approximation when the measured diameter and length direction thermal expansion coefficients are known. The single helix model illustrates the sensitivity...
In this work we study the rheology of polymeric brushes at the nanoscale interacting with an explicitly included atomic force microscopy (AFM) tip, using dissipative particle dynamics simulations, as models for pericellular brushes on epithelial cells. Two types of cells brushes are modeled: normal cells, whose surface is covered by brushes of uniform length, and cancer cells, which are covered by...
We developed a reactive coarse-grained model for chain-growth polymerization to study the chain length distribution of polymers grafted from a surface as compared to those grown in solution. The surface-initiated polymer chains exhibit a markedly broader distribution of chain lengths (larger dispersity) and slower chain growth kinetics as compared to the solution phase process. Two key factors that...
Dispersion in polymer nanocomposites is determined by the kinetics of mixing and chemical affinity. Compounds like reinforcing filler/elastomer blends display some similarity to colloidal solutions in that the filler particles are close to randomly dispersed through processing. It is attractive to apply a pseudo-thermodynamic approach taking advantage of this analogy between the kinetics of mixing...
Traditionally, in situ polymerization has been used to make polymer-carbon nanotube composites. Here, we report a simple method of mixing polyaniline with single-walled carbon nanotubes in a variety of organic solvents via ultrasonication. The maximum loading fraction of SWCNTs in the composites is determined by the conformation of the polyaniline chains. The type of solvent used has the greatest...
We study the possibility of the spinodal decomposition in the induction period of the polymer crystallization. This phenomenon was first reported in an X-ray scattering experiment, and has still been controversial due to various experiments and theories that support or deny the phenomenon. In this article, we explain the condition for the spinodal decomposition to occur in polymer melts by deriving...
Graphene oxide (GO) synthesized from graphite via oxidation and exfoliation is a graphene-like single-layer sheet with numerous oxygen groups and defects on the basal plane. In this study, GO is added as a filler in the polyvinyl alcohol (PVA) matrix for the purpose of improving thermal conductivity. GO is well dispersed in PVA aqueous solution, and GO/PVA composite films are easily prepared with...
Cationic polymerization of two styrene derivatives containing carbazole moiety with different linking topology, 9-(4-vinylphenyl)carbazole (M1) and 3-(4-vinylphenyl)-9-ethylcarbazole (M2), using 1-chloro-1-phenylethane (PhEtCl)/SnCl4 initiating system has been investigated. It was shown that polymerization of M1, which is characterized by higher electron density on the carbon at the 3 position of...
This study reports on the effects of the matrix's crystal type (α or γ crystal) and chain mobility on the electrical properties of polypropylene (PP)/carbon nanotube (CNT) composites. Isothermal crystallization of the composites was performed at various temperatures and under atmospheric and elevated pressures with supercritical carbon dioxide (scCO2). Remarkably, experimental results indicated that...
The crystallographic micromechanical model (CMM) for prediction of yield stress of semicrystalline polymers, based on the thermally activated nucleation of screw dislocations at the boundary of lamellar crystals, is employed to interpret the yield behavior by effect of uniaxial drawing of some isotactic copolymers of propylene with different comonomeric units such as ethylene, 1-butene, 1-pentene,...
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