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We have carried out various rheometric experiments to probe the nonlinear rheological behavior of two well-entangled 1,4-polybutadiene solutions using both stress-controlled and rate-controlled startup shear. At a polymer concentration of 2% neither wall slip nor shear banding occurs, and there is no visible edge failure. At a moderate level of shear stress, the shear rate can take an induction time...
We carry out simultaneous mechanical and IR-thermal-imaging based temperature measurements of SBR melts during uniaxial extension in order to delineate the nature of the observed mechanical responses. Using the first law of thermodynamics, we evaluate the enthalpy change h1 associated with the temperature rise in the extending melt, estimate the heat loss to the surrounding, and conclude that there...
We carry out simultaneous mechanical and IR-thermal-imaging-based temperature measurements of tensile extension on untreated, milled (mechanically “rejuvenated”) and melt-stretched bisphenol A-polycarbonate (PC). The extension is found to cause significant buildup of both excess internal energy u2 and plastic dissipation. The magnitude of u2 is one to two orders of magnitude higher than the energy...
We study nonlinear stress relaxation behavior of several polymer glasses during ductile large deformation of either extension or compression over a wide range of deformation rate at room temperature. In the pre-yield regime, the stress decline is logarithmically slow and essentially independent of the applied rate. The stress relaxation from the post-yield regime shows universal time rescaling, i...
We report the synthesis of oligothiophene-containing polymer brushes and their application as nanodielectric materials in capacitors. Specifically, terthiophene-containing methacrylate polymer brushes were synthesized via a “graft from” technique by a combination of ring-opening metathesis polymerization (ROMP) and reversible addition fragmentation chain transfer (RAFT) polymerization. Both X-ray...
We explored a new synthetic strategy for ultra-high molecular weight long-chain branched (LCB) polymers with equal spacing between adjacent branch points. This method can synthesize LCB polystyrene (LCB-PS) with total molecular weight of 4.9 million g/mole, 16 branches of 140 kg/mole and polydispersity index of 1.5. The introduction of multiple branch points with long side chains allows the LCB-PS...
We apply a constant tensile load (i.e., fixed engineering stress) at different temperatures to examine the mechanical and structural responses of polycarbonate (PC) glass. Unlike the more common displacement-controlled extension, the tensile creep test allows the glass to develop structural failures on its time scales. At room temperature, surface crazes over time at sufficiently high tensile loads,...
A series of ferroelectric poly(vinylidene fluoride-co-chlorotrifluoroethylene) films with different crystallite sizes have been obtained by varying the film processing conditions. The impact of the crystallite size on the dipole switching and the electric energy density has been systematically studied by the electric displacement–electric field hysteresis loop measurements. The films with smaller...
This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon...
Exfoliated polystyrene (PS)/organo-modified montmorillonite (MMT) nanocomposites were synthesized through in situ free radical bulk polymerization by dispersing a modified reactive organophilic MMT layered silicate in styrene monomer. The original MMT was modified by a mixture of two commercial cationic surfactants, [2-(acryloyloxy)ethyl](4-benzoylbenzyl)dimethylammonium bromide (ADAB) and cetyltrimethylammonium...
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