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Abstract: Thermal polymerization of methyl (meth)acrylate (MMA) was carried out using 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) and cumyl dithionaphthalenoate (CDN) as chain transfer agents. The kinetic study showed the existence of induction period and rate retardation, especially in the CDN mediated systems. The molecular weights of the polymers increased linearly with the monomer conversion, and the molecular weight distributions (M w/M ns) of the polymers were relatively narrow up to high conversions. The maximum number-average molecular weights (M ns) reached to 351 900g/mol (M w/M n =1.47) and 442 400g/mol (M w/M n =1.29) in the systems mediated by CPDN and CDN, respectively. Chain-extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA-block-polystyrene (PMMA-b-PSt) copolymer with controlled structure and narrow M w/M n. Thermal polymerization of methyl acrylate (MA) in the presence of CPDN, or benzyl (2-phenyl)-1-imidazolecarbodithioate (BPIC) also demonstrated “living”/controlled features with the experimented maximum molecular weight 312 500g/mol (M w/M n =1.57). The possible initiation mechanism of the thermal polymerization was discussed. [Copyright &y& Elsevier]

Modulating on‐demand polymerization is a challenge in synthetic macromolecules. Herein, tailoring polymerization controllability and dispersity during single‐electron transfer mediated living radical polymerization (SET‐LRP) of methyl methacrylate (MMA) is achieved. Hexaarylbiimidazole (HABI) is employed as a photoswitchable catalyst, allowing reversible control of catalytic activity between an active and inactive state. In the presence of HABI and with the light on (active state), control SET‐LRP of MMA follows first‐order kinetics, resulting in polymers with a narrow molecular weight distribution. In contrast, polymerization responds to light and reverts to their original uncontrolled state with light off (inactive state). Therefore, repeatable resetting polymerization can be easily performed. The key to photomodulating dispersity is to use an efficient molecular switch to tailor the breadths of dispersity. Besides, the mechanism of HABI‐mediated SET‐LRP with switchable ability is proposed. [ABSTRACT FROM AUTHOR]

Photo-induced reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile was performed in a two-component system using 2-cyano-2-propyl dodecyl trithiocarbonate as the initiation-regulator dual-functional agent. The polymerization was carried out under mild conditions, e.g. under irradiation of blue light-emitting diode light at ambient temperature. Well-controlled polymers with high molecular weight and narrow molecular weight distribution were obtained. The light on and off experiments showed photosensitivity of this polymerization system. The structure of the obtained polymers was characterized by GPC and NMR. Polymers with molecular weight as high as M n = 286,300 g/mol could be obtained in optimized conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT The living free radical polymerizations of vinyl acetate (VAc) were successfully achieved in the presence of a novel organic selenium compound (diselenocarbonates), with 2,2′-azobisisobutyronitrile (AIBN) as the initiator. The living characteristics of the VAc polymerization were confirmed by the linear first-order kinetic plots and linear increase of molecular weights ( Mn) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions. In addition, the end of the polymers contains selenium element which may be useful in biotechnological and biomedical applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3159-3165 [ABSTRACT FROM AUTHOR]

Abstract: Well-defined photo-responsive alternating copolymers, poly(4-(N-maleimido)azobenzene-alt-styrene)s (PMSts), were successfully synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. A divinyl monomer was used in this polymerization to prepare high molecular weight azobenzene polymers. These polymers had good solubility in most organic solvents, formed films well, and had high glass transition temperatures (T g =174–250°C) and were heat resistant (T d >320°C). The photo-induced trans–cis isomerization of the copolymers was examined in chloroform solution. Surface-relief-gratings (SRGs) formed on the polymer films were also investigated using illumination from a linearly polarized Kr+ laser beam. [Copyright &y& Elsevier]

Polymer molecular weight distribution (MWD) is a key parameter of polymers. Here we present a robust method for controlling polymer MWD in controlled cationic polymerizations. A latent mediator strategy was designed and combined with temporal programming to regenerate mediators at different times during polymerization. Both the breadths and shapes of MWD curves were tuned easily by adjusting an external light source. Bimodal, trimodal, and tetramodal distributions were obtained, and the breadths could be varied from 1.06 to 2.09. Polymers with different MWDs prepared by this method had good chain end fidelity, which was demonstrated with successful chain‐extension experiments. In addition, the introduction of temporal programming with a computer‐controlled single chip for the light source opened an avenue for the use of artificial intelligence in polymer synthesis. [ABSTRACT FROM AUTHOR]

Polymer molecular weight distribution (MWD) is a key parameter of polymers. Here we present a robust method for controlling polymer MWD in controlled cationic polymerizations. A latent mediator strategy was designed and combined with temporal programming to regenerate mediators at different times during polymerization. Both the breadths and shapes of MWD curves were tuned easily by adjusting an external light source. Bimodal, trimodal, and tetramodal distributions were obtained, and the breadths could be varied from 1.06 to 2.09. Polymers with different MWDs prepared by this method had good chain end fidelity, which was demonstrated with successful chain‐extension experiments. In addition, the introduction of temporal programming with a computer‐controlled single chip for the light source opened an avenue for the use of artificial intelligence in polymer synthesis. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: The on‐demand building copolymer structures, from sequence to architecture, is crucial in understanding the relation between polymer structure and property, meanwhile motivating the innovation of polymer hierarchy. However, the challenge is conspicuous for complicated polymer structures from inherently intricate polymerization. In this work, copolymers with tailored grafting density and distributions were achieved using successive latent monomer and grafting‐from strategies. The hydroxyl group functionalized furan/maleimide adduct (FMOH) was selected as the latent monomer for RAFT polymerization of an array of copolymers with tailored localization of hydroxyl group along the main chain. The hydroxyl group further initiated the ring opening polymerization (ROP) of L‐lactide or ε‐caprolactone, resulting in a library of multicomponent copolymers via grafting‐from strategy. The initiating efficiency reached to ~100% with variable molecular weight (21300—58600 Da) and narrow distributions (ÐM < 1.25), indicating that such graft copolymers possessed controlled density and distribution of side chains as its linear template. The investigation on thermal properties of the well‐defined graft copolymers implied that the precise tailoring over copolymer structures at the molecule level could lead to tunable chemical/physical properties. This work bridged polymer from sequence to architecture, unveiled a new method in creating graft copolymers with programmable structures and provided the insight into the structure/property relationship. [ABSTRACT FROM AUTHOR]

A series of self-assembled 1D nanostructures, including straight and helix nanofibers, nanoribbons, and nanobelts, were fabricated from uniform amphiphilic azobenzene oligomers with tunable molecular weight and side chain functionality, promoted by multiple and cooperative supramolecular interactions. Additionally, the morphological transformation of the nanofibers was achieved during the photoisomerization process. [ABSTRACT FROM AUTHOR]

Cyclic polymers, having no chain ends, are in contrast to their linear counterparts with respect to topology and related properties. While the behavior of cyclic polymers in solution is well investigated, there is little information on the effects of cyclic chain topology on surfaces grafted with these polymers. In particular, the effects of topology on the interactions of such surfaces with biological systems are unknown. In this work, we prepared gold surfaces modified with either cyclic or linear polystyrene (CPS, LPS) using a grafting-to strategy, and used these surfaces to investigate the effects of chain topology on their biointerfacial interactions. It was shown that compared to LPS with similar molecular weight, the smaller hydrodynamic radius of CPS leads to brushes of higher chain density, and that the higher chain density facilitates the adsorption of larger proteins but suppresses the adsorption of smaller ones. However, no significant differences in bacterial attachment or mammalian cell proliferation between CPS and LPS brushes were found, indicating that topological effects are absent for the larger entities. [ABSTRACT FROM AUTHOR]

Vinyl acetate is polymerized in the living way under the irradiation of blue light-emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2-(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well-regulated molecular weight and narrow molecular weight distribution (Ð < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix-assisteed laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). [ABSTRACT FROM AUTHOR]

A novel Janus compound containing azo-based thermal initiator and bromo-based atom transfer radical polymerization (ATRP) initiator group is synthesized. Such compound can be applied in the living radical polymerization of alkyl methacrylate monomers, such as methyl methacrylate, tert-butyl methacrylate, and 2-( N, N-dimethylamino) ethyl methacrylate. Polymers with controlled molecular weights and narrow molecular weight distributions are obtained. The structure of polymers is identified by 1H NMR spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrum. A modified initiator for continuous activator regeneration ATRP mechanism is proposed according to the polymerization behavior, hydrolysis of chain backbone, and end group identification. [ABSTRACT FROM AUTHOR]

[Display omitted] • First microflow cationic polymerization under ambient conditions. • No further purification of all reagents were required. • Well-defined poly(vinyl ether)s can be achieved within 2 min. Living cationic polymerization is a well-established method for preparing polymers with controlled molecular weights and complex architectures, but rigorous polymerization conditions limit its widespread application. Here, we report a facile strategy for simplifying the strict conditions required for traditional living cationic polymerizations of various vinyl ethers including ethyl vinyl ether (EVE), propyl vinyl ether (PVE), butyl vinyl ether (BVE) and isobutyl vinyl ether (IBVE) by utilizing continuous microflow reactors and a weak Lewis acid, zinc chloride (ZnCl 2). Well-defined polymers with controlled molecular weights and narrow molecular weight distributions (<1.20) can be obtained under ambient conditions without monomer purification, temperature control or strictly anhydrous conditions. The living nature of the polymerization was verified by kinetic experiments and successful in situ chain extension. [ABSTRACT FROM AUTHOR]

Abstract: The optimal conditions for the hydrogen bonding interaction between 4-vinylpyridine (4VP) and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) were screened via UV-vis spectroscopy. The results demonstrated that equimolar 4VP and HFIP, and temperature at 25 °C favored a better hydrogen bonding interaction. Guided by these primary results, the room-temperature Cu(0)-mediated controlled radical polymerization was selected for the controlled polymerization of 4VP in the presence of equiv. HFIP. The polymerizations produced polymers with more predictable number-average molecular weights (M n ,SEC) and narrower molecular weight distributions (M w /M n <1.25) in comparison with those without hydrogen bonding interaction. Moreover, the hydrogen bonding had profound impacts on the stereoregulation during polymerization, which enabled P4VP with a highly syndiotactic (60.2%) and gave rise to a higher glass transition temperature (T g ) of P4VP. [Copyright &y& Elsevier]

Abstract: The light sensitive vinyl monomer with coumarin unit, 7-(4-(acryloyloxy)butoxy)coumarin (7AC), was synthesized. The reversible addition–fragmentation chain transfer (RAFT) polymerization of 7AC, initiated by 2,2′-azobisisobutyronitrile (AIBN), was carried out using 2-cyanoprop-2-yl dithiobenzoate (CPDB) as a RAFT agent in N,N-dimethylformamide (DMF) solution. The kinetics exhibited first-order relationship with respect to the monomer concentration. The molecular weight of the polymer increased linearly with the monomer conversion. The chain extension of poly(7-(4-(acryloyloxy)butoxy)coumarin) (P7AC) using styrene (St) as the second monomer demonstrated that the obtained polymers were almost “living”. The fluorescence intensity of P7AC increased with the molecular weight of P7AC and was stronger than that of the monomer. The obtained polymer had strong ultraviolet (UV) absorption at 322nm. The molecular weights of the polymer had no effect on its ultraviolet absorption intensity. The coumarin structure existing in P7AC underwent [2+2] cycloaddition reaction (photodimerization) under UV irradiation in tetrahydrofuran (THF) solution, which can be further used to prepare small particles from the single polymer. [Copyright &y& Elsevier]

Carbohydrates play an important role in biological processes for their specific interactions with proteins. Cyclic glycopolymers are promising to mimic the topology of natural macrocycle–biomacromolecules due to their unique architecture of lacking chain ends. To systematically study the effect of glycopolymer architecture on the interactions with protein, the cyclic glycopolymers bearing galactose side‐chain (cyclic PMAGn) with three degrees of polymerization (n = 14, 24, 47) are prepared for the first time. The cyclic PMAGn exhibits unique properties in agglutinating and inhibiting proteins in subsequent studies by comparison with the linear precursor with the same molecular weights. More impressively, the cyclic PMAGn highlight the improved performance of cyclic architecture. For example, the cyclic PMAGn shows superior inhibition abilities to suppress amyloid formation from amyloid β protein fragment 1‐42 aggregation and block the specific interaction between bacteria and galactose‐modified surface compared to that of respective linear counterpart. This interesting finding suggests that the architecture of cyclic glycopolymers may be capable of optimizing the ability to bind or inhibit proteins in biological processes. [ABSTRACT FROM AUTHOR]