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In order to predict scratch performance of polymers, the present study focuses on quantitative assessment of various scratch-induced deformation mechanisms based on a set of model amorphous polymers via numerical modeling. A modification of Ree-Eyring theory is used to account for the rate dependent behavior of the model polymers at high strain rates using the experimental data obtained at low strain...
Under effect of annealing and reinforcement of carbon fiber (CF), the relationship between crystalline structure of polyamide 6 (PA6) and thermal/mechanical properties was well studied. A local thermal analysis (LTA) method was applied for detecting interface properties between CF and PA6. Significant enhancement of thermal properties of PA6 with annealing and CF reinforcement was confirmed by thermal...
Covalent adaptable networks (CANs) are cross-linked polymers capable of relieving internal stresses by reconfiguring their network topology. Specifically, reversible addition-fragmentation chain transfer (RAFT) is a mechanism by which covalent bonds are exchanged to relieve internal stresses. While stress relaxation in such systems has been studied in bulk materials, here, we characterize the ability...
Self cure promoting, amine-containing novolac–phthalonitrile (APN) resins of varying compositions were synthesized and characterized. APN possessing amine functionalities reduced the cure initiation temperature from 310 °C (typical of pure phthalonitrile systems) to 180 °C. It showed excellent thermal stability up to 420 °C and high char residue of 77–79 %. Co-reaction of APN with diglicydyl ether...
During a cyclic tension test, many elastomeric materials exhibit an appreciable softening in their mechanical properties resulting from the previous stretch, known as the Mullins effect. This paper explores the influence of the stretch induced softening effect to the free recovery behavior of an acrylate shape memory polymer (SMP) composite by incorporating carbon black (CB) as filler materials. The...
Wireless transduction of light into mechanical work manifested as shape-changing surfaces, adaptive structures, or actuators is a topic of considerable recent interest. In the work reported here, the photomechanical responses of a new series of crosslinked azobenzene-functionalized polyimides prepared with increasing backbone rigidity over a range of crosslinker concentrations are examined. The baseline...
The enzymatic degradation of textile dyes offers an alternative approach over the conventional waste water treatment processes. Covalent immobilization of the enzymes onto insoluble supports not only permits their reusability and easy separation of enzymes from the product but also, if properly performed, may improve their activities, stability and hence reduces the cost of process. In the present...
We have demonstrated the site-specific thermal activation of self-immolative polymers (SIPs) using a bicyclic oxazine as a temperature-sensitive triggering moiety. The oxazine-based trigger was installed at the junction of a SIP-poly(N,N-dimethylacrylamide) (PDMA) diblock copolymer via oxidation of hydroxyurea end groups on the SIP and in situ [4 + 2] cycloaddition with cyclopentadiene-functionalized...
The goal of this research is to synthesize the hyperbranched polythiophene derivatives (P1 and P4) containing tetrachloroperylene bisimide as bridging moiety for investigation of thermal, electrochemical, and opto-electrical properties of these derivatives. The polymers (P2 and P3) containing soft alkyl spacer as bridging moiety and linear poly(3-hexylthiophene) (P3HT) were also synthesized for comparison...
Polymer gels undergoing the oscillating Belousov-Zhabotinsky (BZ) reaction exhibit an autonomous, periodic swelling and deswelling, where the mechanical oscillations are driven by the chemical reaction within the polymer network. Using computer simulations, we show that these BZ gels can undergo a form of auto-chemotaxis, enabling the gels to spontaneously move in response to self-generated chemical...
The covalent integration of inorganic nanoparticles in polymer matrices has gained significance for improving the structural properties of polymer-based materials. Here we report on the performance of poly(ω-pentadecalactone) networks with magnetite nanoparticles as netpoints in their magnetically-controlled shape-memory capability. Hybrid nanocomposites with magnetite nanoparticle content ranging...
Shape-memory surfaces with on demand, tunable nano-patterns have been developed to observe time dependent changes in fibroblast cell alignment using temperature-responsive poly(ε-caprolactone) (PCL) films. The PCL films were prepared by crosslinking tetra-branched and linear PCLs, each with acrylate end-groups. Permanent surface patterns were generated by crosslinking the PCLs in a mold. Temporary...
Poly(N-vinylcarbazole) (PNVK) is one of the extensively studied photoconductive polymers because of its wide ranges of applications. Through the reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthates (RAFT/MADIX) polymerizations, in this study we investigated the syntheses of PNVK-based block copolymers (BCPs) with styrene (St) and methyl methacrylate...
A promising candidate for the development of stimuli-responsive morphing materials are based on liquid crystal polymer networks. These anisotropic materials will contract along the alignment director and expand perpendicular to it when subjected to an anisotropy-reducing stimulus, such as heat. As the liquid crystals can be aligned prior to polymerization using various alignment techniques, it is...
Using a unique slit flow device and in situ synchrotron X-ray methods, the entire evolution of flow induced crystallization in isotactic polypropylene (iPP) was studied from the start-up of flow up to completion of crystallization. Two WAXD detectors, including the ultrafast Pilatus and the two-dimensional Frelon, were combined to achieve a sufficient time resolution for a fairly short period (during...
A monomer, 2-(isobutyramido)-3-methylbutyl methacrylate (IMMA) was synthesized through a two-step reaction. When a few of IMMA (less than 4 mol%) was copolymerized with N-vinylimidazole (VIm) under free radical polymerization condition, water-soluble P(VIm-co-IMMA) copolymers were obtained. Their structural information was verified and interpreted from 1H NMR, FTIR and GPC. Kinetic analyses from 1...
This work aims to improve the performance of air-breathing microbial fuel cells (MFCs) through using hydrocarbon polymer based nanocomposite proton exchange membranes. Accordingly, nanocomposite membranes based on sulfonated poly(ether ether ketone) (SPEEK) and montmorillonite (MMT) were investigated for such an application. Although the incorporation of MMT into SPEEK membranes resulted in reduced...
Well-defined amphiphilic block copolymers composed of S-vinyl sulfides and N-isopropyl acrylamide (NIPAM) were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. Thermoresponsive core–shell nanoparticles with cross-linked π-conjugate cores were obtained by in situ cross-linking reactions between 4-bromophenyl moieties in the block copolymers and diboronic acids...
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