Showing papers in "Journal of Polymer Science Part A in 2018"

High sulfur content polymers: The effect of crosslinker structure on inverse vulcanization.

Abstract: Inverse vulcanized high sulfur content polymers have attracted much attention recently due to their potentially low cost and diverse applications. More than 60 million tonnes of excess sulfur are produced annually by hydrodesulfurization of crude oil and gas. 1 Conventional uses of sulfur only use a fraction of this supply. Production of polymeric materials from sulfur would alleviate this, but pure sulfur polymers are unstable and depolymerize back to S8.1 However, “inverse vulcanization,” first reported by Pyun and coworkers,2 allows the stabilization of sulfur polymers by a small organic molecule that acts as a crosslinker against depolymerization, such as 1,3‐diisopropenylbenzene (DIB) [Fig. ​[Fig.1(a,b)].1(a,b)]. S‐DIB is a shape persistent and stable copolymer. However, DIB is relatively expensive in comparison with sulfur, and there has been interest to use lower cost crosslinkers, such as limonene [Fig. ​[Fig.11(b)].3 Limonene has many advantages; being bioderived, renewable, and economic. However, the sulfur–limonene polymer formed was a low molecular weight polysulfide, rather than a fully crosslinked high molecular weight polymer, and is not shape persistent [Supporting Information Fig. S1], which may limit some applications. Similarly, dicyclopentadiene (DCPD), an industrial by‐product, has been shown to produce stable polymers with sulfur, forming a hard brittle solid [Fig. ​[Fig.11(b)].4 It is also unclear why very structurally similar crosslinkers, in terms of molecular mass and degree of unsaturation, produce materials of dramatically different properties after reaction with sulfur, that is, from viscous liquids to rubbery or glassy solids. Open in a separate window Figure 1 Inverse vulcanization reaction of elemental sulfur and crosslinker, where R indicates an organic molecule with unsaturated bonds (b) From left to right: limonene, ENB, DIB, and DCPD. T gs given below the crosslinkers are for 50 wt % to 50 wt % copolymers of the crosslinkers and sulfur. It can be noted that although the crosslinkers have similar molecular mass, and the same degree of unsaturation, they show markedly different properties. [Color figure can be viewed at http://wileyonlinelibrary.com]

Efficient photopolymerization of thick pigmented systems using upconversion nanoparticles-assisted photochemistry

Abstract: Photopolymerization of thick pigmented systems still remains challenging due to the light screening effect of the pigments. Here, we present a facile method based on upconversion nanoparticles (UCNPs)-assisted photochemistry to achieve efficient photopolymerization and improved curing depth of pigmented systems. Under a 980-nm laser irradiation, UCNPs are able to convert NIR light into UV and visible light to activate photoinitiators for the initiation of polymerization. Influencing factors on photopolymerization were systematically investigated. With optimal parameters, 25.5 mm of photopolymerization depth combined with 70% of maximal double bond conversion was obtained. The peak temperature of 120.4 °C during UCNPs-assisted photopolymerization is comparable with or lower than that of some reported frontal photopolymerization applied to prepare functional composite polymeric materials. Both indentation hardness and reduced modulus of the photocured materials using UCNPs as internal lamps were higher than those of the reference cured under traditional blue LED light. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018

Blocky poly(ɛ‐caprolactone‐co‐butylene 2,5‐furandicarboxylate) copolyesters via enzymatic ring opening polymerization

Abstract: Cyclic oligo(butylene 2,5-furandicarboxylate) and e-caprolactone were copolymerized in bulk at 130-150 oC by enzymatic ring opening polymerization using CALB as catalyst. Copolyesters within a wide range of compositions were thus synthesized with weight-average molecular weights between 20,000 and 50,000, the highest values being obtained for equimolar or nearly equimolar contents in the two components. The copolyesters consisted of a blocky distribution of the e-oxycaproate (CL) and butylene furanoate (BF) units that could be further randomized by heating treatment. The thermal stability of these copolyesters was comparable to those of the parent homopolyesters (PBF and PCL), and they all showed crystallinity in more or less degree depending on composition. Their melting and glass-transition temperatures were ranging between those of PBF and PCL with values increasing almost linearly with the content in BF units. The ability of these copolyesters for crystallizing from the melt was evaluated by comparative isothermal crystallization and found to be favored by the presence of flexible e-oxycaproate blocks. These copolyesters are essentially insensitive to hydrolysis in neutral aqueous medium but they became noticeably

Fabrication of poly(vinyl alcohol)‐graphene quantum dots coated with poly(3,4‐ethylenedioxythiophene) for supercapacitor

Abstract: Conducting nanofiber composed of poly(vinyl alcohol) (PVA), graphene quantum dots (GQDs) and poly(3,4-ethylenedioxythiophene) (PEDOT) was prepared for symmetrical supercapacitor through electrospinning and electropolymerization techniques The formation of PVA nanofibers with the addition of GQDs was excellently prepared with the average diameter of 5566 ± 27 nm Field emission scanning electron microscopy images revealed that cauliflower-like structure of PEDOT was successfully coated on PVA-GQD electrospun nanofibers PVA-GQD/PEDOT nanocomposite exhibited the highest specific capacitance of 29186 F/g compared with PVA/PEDOT (22073 F/g) and PEDOT (16148 F/g) PVA-GQD/PEDOT also demonstrated a high specific energy and specific power of 1695 and 98448 W/kg, respectively, at 20 A/g current density PVA-GQD/PEDOT exhibited the lowest resistance of charge transfer (Rct) and equivalent series resistance compared with PEDOT and PVA/PEDOT, indicating that the fast ion diffusion between the electrode and electrolyte interface PVA-GQD/PEDOT nanocomposite also showed an excellent stability with retention of 98% after 1000 cycles © 2017 Wiley Periodicals, Inc J Polym Sci, Part A: Polym Chem 2017

Medium band gap conjugated polymers from thienoacene derivatives and pentacyclic aromatic lactam as promising alternatives of poly(3-hexylthiophene) in photovoltaic application

Abstract: Two alternating medium band gap conjugated polymers (PBDT-TPTI and PDTBDT-TPTI) derived from 4,8-bis(4,5-dioctylthien-2-yl)benzo[1,2-b:4,5-b′]dithiophene (BDT-T) or 5,10-bis(4,5-didecylthien-2-yl)dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT-T) with pentacyclic aromatic lactam of N,N-didodecylthieno[2′,3′:5,6]pyrido[3,4-g]thieno[3,2-c]-iso-quinoline-5,11-dione (TPTI), are synthesized and characterized. The comparative investigation of the photostabilities of the copolymers revealed that the PDTBDT-TPTI film exhibited the comparable photostability in relative to P3HT. Meanwhile, the inverted photovoltaic cells (i-PVCs) from the blend films of PBDT-TPTI and/or PDTBDT-TPTI with PC71BM, in which poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] were used as cathode modifying interlayer, presented higher power conversion efficiencies (PCEs) of 5.98% and 6.05% with photocurrent response ranging from 300 nm to 650 nm in contrast with the PCEs of 4.48% for the optimal inverted PVCs from P3HT/PC71BM under AM 1.5 G 100 mW/cm2. The PCEs of the i-PVCs from PBDT-TPTI and PDTBDT-TPTI were improved to 7.58% and 6.91% in contrast to that of 0.02% for the P3HT-based i-PVCs, and the photocurrent responses of the devices were extended to 300–792 nm, when the ITIC was used as electron acceptor materials. The results indicate that the PBDT-TPTI and PDTBDT-TPTI can be used as the promising alternatives of notable P3HT in the photovoltaic application. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.

Self-sustained actuation from heat dissipation in liquid crystal polymer networks

Abstract: Liquid crystal polymer networks (LCNs) lead the research geared toward macroscopic motion of materials. These actuators are molecularly programed to adapt their shape in response to external stimuli. Non-photo-responsive thin films of LCNs covered with heat absorbers (e.g., graphene or ink) are shown to continuously oscillate when exposed to light. The motion is governed by the heat dissipated at the film surface and the anisotropic thermal deformation of the network. The influence of the LC molecular alignment, the film thickness, and the LC matrix on the macroscopic motion is analyzed to probe the limits of the system. The insights gained from these experiments provide not only guidelines to create actuators by photo-thermal or pure photo-effects but also a simple method to generate mechanical oscillators for soft robotics and automated systems. © 2018 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1331-1336.

Moisture-mediated intrinsic self-healing of modified polyurethane urea polymers

Abstract: Functional materials having the ability to self-heal cracks or scratches after damage are of great interest for a huge scope of applications. Herein, we report a self-healing polyurethane urea-based material with implemented 1-(2-aminoethyl) imidazolidone (UDETA) as a chain terminating molecule and for hydrogen bond network formation. Both, UDETA content and moisture affected the self-healing process. The reversible change in the materials properties was proven by detailed analyses of hardness and thermomechanical behavior in dependence of the water uptake of the samples. FT-IR analysis revealed that water is able to act as a plasticizer interrupting hydrogen bonding interactions within the polymer network and thus, influencing glass transition temperature and hardness of the samples. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 537–548.

Double thermoresponsive block–random copolymers with adjustable phase transition temperatures: From block-like to gradient-like behavior

Abstract: Stimuli-responsive block–random copolymers are very useful “smart” materials as their switching behavior can be tuned by simply adjusting the composition of the random copolymer block. Because of that, we synthesized double thermoresponsive poly(N-acryloylpyrrolidine)-block-poly(N-acryloylpiperidine-co-N-acryloylpyrrolidine) (PAPy-b-P(APi-co-APy)) copolymers via reversible addition fragmentation chain transfer (RAFT) polymerization and investigated their temperature-induced self-assembly in aqueous solution. By varying the APi/APy ratio in the random copolymer block, its phase transition temperature (PTT1) can indeed be precisely adjusted while the temperature-induced collapse upon heating leads to a fully reversible well-defined micellization. By making the two blocks compositionally similar to more than 60%, the polymers' mechanistic thermoresponsiveness can furthermore be changed from block-like to rather gradient-like behavior. This means the micellization onset at PTT1 and the corona collapse at the PTT of the more hydrophilic pure PAPy block (PTT2) overlap resulting in one single broad transition. This work thus contributes to the detailed understanding of design, synthesis and mechanistic behavior of tailored “on-demand” switchable materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017.

Conjugated Carbazole-Based Schiff Bases as Photoinitiators: From Facile Synthesis to Efficient Two-Photon Polymerization

Abstract: Exploration of simple and economical synthetic routes to construct active two‐photon initiators (2PIs) with long conjugation length is highly desirable to promote the development of two‐photon‐induced photopolymerization technology. In this article, several conjugated carbazole‐based derivatives containing N=C bonds as π bridges and electron donor/acceptor groups were prepared through one‐step Schiff base reaction. The structure–activity relationship was systematically investigated through calculations and experimental tests. The results showed that compared to the D‐π‐D‐π‐D molecules, the A‐π‐D‐π‐A molecules exhibited stronger charge transfer, which induce redshifted linear absorption and enhanced two‐photon absorption at 800 nm. The 2PIs displayed aggregation‐induced emission property and show potential for the fabrication of luminescent microdevices. In two‐photon‐induced microfabrication tests, the formulations containing novel 2PIs exhibited lower threshold energy than the widely used commercial photoinitiator Irgacure 369 and the two‐photon resists IP‐L is the brand name of the two‐photon resist from Nanoscribe, specially designed for nanoscribe's laser lithography systems. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2692–2700

Highly proton conducting proton-exchange membranes based on fluorinated poly(arylene ether ketone)s with octasulfonated segments

Abstract: A new bisphenol monomer containing a pair of electron-rich tetra-arylmethane units was designed and synthesized. Based on this monomer, along with commercial 4,4′-(hexafluoroisopropylidene)diphenol A and 4,4′-difluorobenzophenone, a series of novel poly(arylene ether ketone)s containing octasulfonated segments of varying molar percentage (x) (6F-SPAEK-x) were successfully synthesized by polycondensation reactions, followed by sulfonation. Tough, flexible, and transparent membranes, exhibiting excellent thermal stabilities and mechanical properties were obtained by casting. 6F-SPAEK-x samples exhibited appropriate water uptake and swelling ratios at moderate ion exchange capacities (IECs) and excellent proton conductivities. The highest proton conductivity (215 mS cm−1) is observed for hydrated 6F-SPAEK-15 (IEC = 1.68 meq g−1) at 100 °C, which is more than 1.5 times that of Nafion 117. Furthermore, the 6F-SPAEK-10 membrane exhibited comparable proton conductivity (102 mS cm−1) to that of Nafion 117 at 80 °C, with a relatively low IEC value (1.26 meq g−1). Even under 30% relative humidity, the 6F-SPAEK-20 membrane (2.06 meq g−1) showed adequate conductivity (2.1 mS cm−1) compared with Nafion 117 (3.4 mS cm−1). The excellent comprehensive properties of these membranes are attributed to well-defined nanophase-separated structures promoted by strong polarity differences between highly ionized and fluorinated hydrophobic segments. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017

Sustainable, fire-resistant phthalonitrile-based glass fiber composites

Abstract: The sustainable resveratrol-based phthalonitrile was used in the preparation of E-glass fiber-reinforced phthalonitrile composite panels fabricated by hot pressed prepreg consolidation with bis[4-(3-aminophenoxy)phenyl]sulfone (m-BAPS) as the curing additive. This amorphous monomer exhibited excellent viscosities at temperatures below 200 °C, which is applicable to standard processing conditions. Rheometric measurements were used to evaluate the cure of the composite as a function of the postcure conditions. The composite retains >95% of its room temperature storage modulus up to 450 °C based on these postcuring parameters. More importantly, flammability performance of the composite—which was determined in terms of ignitability, heat release, and mass loss rate—excels over other state-of-the-art polymer/glass composites. Even under the most extreme heat fluxes (e.g., 100 kW⋅m−2), the composite performs exceptionally well suggesting that resveratrol-based phthalonitrile composites can be used in fire-resistant applications. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. J. Polym. Sci., Part A: Polym. Chem. 2018