Wolf–Lamb‐type Catalysis in One Pot Using Electrospun Polymeric Catalyst MembranesPretscher, Martin O.; Gekle, Stephan; Agarwal, Seema
doi: 10.1002/marc.201900148pmid: 31070820
Multistep catalytic transformations using incompatible catalysts (Wolf–Lamb‐type) in a one‐pot reaction cascade require site isolation of different catalysts by compartmentalization. In this work, the use of different electrospun catalytic membranes in a modular way as individual compartments is shown for one‐pot Wolf–Lamb‐type reaction cascades. The data are presented for one‐pot cascade reaction sequences catalyzed by acidic and basic membranes made by electrospinning polymeric acid (poly(styrene‐co‐styrene sulfonic acid‐co‐4‐methacryloyl‐oxybenzophen)) and basic (poly(styrene‐co‐4‐vinylpyridine‐co‐4‐methacryloyl‐oxybenzophen)) catalysts, respectively. The two‐step, one‐pot system used is the acidic catalyzed deacetylation of dimethoxybenzylacetale to benzaldehyde, which reacts with ethyl cyanoformate to result in a high yield of product (over 90%) under base‐catalyzed conditions. The reaction kinetics are further monitored and evaluated by using differential equations, showing the necessity of a parameter Δt to represent a retarded start for the second reaction step. The concept provides an easy and upscalable approach for use in Wolf–Lamb‐type systems.
Medium‐Bandgap Conjugated Polymer Donors for Organic PhotovoltaicsSun, Liya; Xu, Xiangfei; Song, Shan; Zhang, Yangqian; Miao, Chunyang; Liu, Xiang; Xing, Guichuan; Zhang, Shiming
doi: 10.1002/marc.201900074pmid: 31131936
Recently, an increasing number of researchers have begun to focus on developing nonfullerene acceptors, so it is very important to synthesize new polymers that are compatible with nonfullerene acceptors. Besides, wide‐ or medium‐bandgap polymer donors could be better to match narrow nonfullerene acceptors. The design of medium‐bandgap (MBG) polymer donors and their application in organic photovoltaics (OPVs) play an important part in the improvement of OPV device performance. This review summarizes the photovoltaic performance of MBG polymers that have been reported during the last decade. Furthermore, their structure–property relationships and device performance are discussed. On the basis of analyzing many polymer structures, guidance toward the design of novel photovoltaic materials might be helpful to understand the basic OPV mechanism and the path towards commercialization.
Hyperbranched Multicyclic Polymer Built from Tailored Multifunctional Monocyclic PrepolymerLiu, Chao; Xu, Wen; Zhang, Hua‐Long; Pan, Cai‐Yuan; Hong, Chun‐Yan
doi: 10.1002/marc.201900164pmid: 31090972
A simple and efficient method to construct a hyperbranched multicyclic polymer is introduced. First, a tailored trithiocarbonate with two terminal anthracene units and three azide groups is successfully synthesized, and this multifunctional trithiocarbonate is used as chain transfer agent (CTA) to afford anthracene‐telechelic polystyrene (PS) via reversible addition‐fragmentation chain transfer (RAFT) polymerization. After that, linear PS is irradiated under 365 nm UV light to achieve the cyclization process. The monocyclic polymer further reacts with sym‐dibenzo‐1,5‐cyclooctadiene‐3,7‐diyne via “A2+B3” strategy based on a self‐accelerating click reaction to produce hyperbranched multicyclic polymer. The structures and properties of the polymers are characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), UV–vis spectrophotometry, and triple‐detection size‐exclusion chromatography (TD‐SEC). The number of monocyclic units of the resultant hyperbranched multicyclic polymer reaches about 21 based on multi‐angle laser light scattering (MALLS) measurements. The plot of intrinsic viscosity versus molecular weight reveals that the α value of the unique hyperbranched multicyclic polymer is lower than both hyperbranched polymers and cyclic polymers.
The Effect of Epoxidation on Strain‐Induced Crystallization of Epoxidized Natural RubberZhang, Xi; Niu, Kaijing; Song, Weixiao; Yan, Shouke; Zhao, Xiuying; Lu, Yonglai; Zhang, Liqun
doi: 10.1002/marc.201900042pmid: 31021434
The effect of epoxidation on strain‐induced crystallization (SIC) of epoxidized natural rubber (ENR) and mechanism are studied with synchrotron radiation wide‐angle X‐ray diffraction (SR‐WAXD) and polarized infrared spectroscopy (P‐IR). WAXD results reveal that appropriate epoxidation, for example, ENR‐25 epoxidized with ≈25% isoprene units, can unexpectedly enhance the SIC of natural rubber (NR), resulting in the improvement of tear resistance. On the other hand, exorbitant epoxidation, for example, ENR‐40 epoxidized with ≈40% isoprene units, depresses the SIC and weakens the mechanical properties of NR remarkably. P‐IR studies reveal that epoxidation can promote the orientation of chain segments along the stretching direction, which plays a determining role on SIC of NR. Accordingly, hierarchical multiscale schematic models are proposed. This insight into epoxidation on SIC of ENR strongly suggests that ENR with appropriate epoxidation degree is a promising candidate material for the fabrication of high‐performance engineering rubber products.
Controlled Synthesis of Block Copolymers by Mechanistic Transformation from Atom Transfer Radical Polymerization to Iniferter ProcessAydogan, Cansu; Ciftci, Mustafa; Yagci, Yusuf
doi: 10.1002/marc.201900109pmid: 31087732
A straightforward transformation protocol combining two distinct living polymerization methods for the controlled synthesis of block copolymers is described. In the first step, bromo‐terminated poly(methyl methacrylate) is prepared by atom transfer radical polymerization (ATRP). Then, a bromide end group is substituted with a triphenylmethyl (trityl) functionality under visible light irradiation using dimanganese decacarbonyl (Mn2(CO)10) photochemistry. The resulting polymers with trityl end groups are used as macroiniferter for the polymerization of styrene and tert‐butyl acrylate (tBA) to yield desired block copolymers with narrow molecular weight distribution. Moreover, the amphiphilic copolymers with acrylic acid functionalities are obtained by the hydrolyzation of poly(tert‐butyl acrylate) containing block copolymers with trifluoroacetic acid.
Synthesis of Stannole‐Containing π‐Conjugated Polymers by Post‐Element Transformation of Organotitanium PolymerMatsumura, Yoshimasa; Sugihara, Masato; Tan, Sia‐Er; Sato, Tatsuhiko; Hayashi, Kohei; Nishiyama, Hiroki; Zhou, Wei‐Min; Inagi, Shinsuke; Tomita, Ikuyoshi
doi: 10.1002/marc.201800929pmid: 31150134
The synthesis of stannole‐2,5‐diyl‐containing π‐conjugated polymers by the post‐element transformation of a regioregular organotitanium polymer is described. For example, a 1,1‐diphenylstannole‐containing polymer is obtained in 83% yield by the reaction of a regioregular organotitanium polymer, which is prepared from 1,4‐bis(2‐ethylhexyloxy)‐2,5‐diethynylbenzene and a low‐valent titanium complex with diphenyltin dichloride at −50 °C to ambient temperature. The number‐average molecular weight and molecular weight distribution (Mn and Mw/Mn) of the stannole‐containing polymer are estimated as 4800 and 1.8, respectively. The obtained polymer is found to have the extended π‐conjugated backbone and relatively low‐lying lowest unoccupied molecular orbital (LUMO) energy level (−3.12 eV), which is supported by its UV–vis absorption spectrum and cyclic voltammetric (CV) analysis. In addition, the stannole‐containing polymer is found to be applicable to a chemosensor for fluoride anion where the color and photoluminescence intensity of the polymer solution exhibits a distinct change in the presence of a fluoride anion.