Phase behavior and Li+ Ion conductivity of styrene‐ethylene oxide multiblock copolymer electrolytes

Solid polymer electrolytes are attractive materials for use as battery separators. Here, a molecular weight series of polystyrene–polyethylene oxide (PEO) multiblock copolymers was synthesized by the thiol–norbornene click reaction. The subsequent materials were characterized both neat and with a lithium bis‐(trifluoromethane)sulfonimide salt loading [(Li)/(EO)] of 0.1. In general, neat samples demonstrated crystallinity scaling with PEO content. Lithium ion‐containing samples had broad scattering peaks, half of which displayed disordered scattering, even at the lowest block molecular weights (polystyrene = 1 kg/mol, PEO = 1 kg/mol). Fitting of disordered scattering data, using the random phase approximation, yielded χ_RPA and R_g values that were compared with recent predictive work by Balsara and coworkers. The predictions were accurate near the volume fraction f_PEO = 0.5 but deviated symmetrically with volume fraction asymmetry. Samples were also analyzed by electrochemical impedance spectroscopy for their potential to conduct lithium ions. Samples with f_PEO ≥ 0.5 demonstrated robust conductivity, whereas samples below this volume fraction conducted very poorly, with one exception (f_PEO = 0.24). This work expanded upon our recently reported approach to multiblock copolymer synthesis, demonstrating the improved access of materials to further our fundamental understanding of multiblock copolymers. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis of graft copolymer of ethyl cellulose through living polymerization and its self-assembly

Copolymers of ethyl cellulose (EC) with polystyrene (PSt) were synthesized through atom transfer radical polymerization (ATRP). The molecular weight of graft copolymers increased without any trace of the EC macro-initiator, and the polydispersity of the side chains was low. The molecular weight of the side chains increased with the monomer conversion. Kinetic study indicated that the polymerization was first order. The micelle characteristics of the graft copolymer in acetone were investigated using dynamic light scattering (DLS), atom force microscopy (AFM) and transmission electron microscopy (TEM). With increasing the concentration, micelles were gradually formed from the solution. The TEM and AFM images indicated that the micelles had spherical shape and showed core-shell structure.     

Studies on the Synthesis of Ethylene Copolymers and Their Properties

The copolymerization of ethylene and 5-ethylidene-2-norbornene (ENB) catalyzed by metallocene catalysts system is reported in this paper. The catalysts include Et(Ind)₂ ZrCl₂/MAO and Cp₂ZrCl₂/MAO. The resulting copolymer contains an ethylidene group which can be readily converted to a hydroxyl group by hydrogen borane. Then the hydroxyl group in turn can be utilized for grafting with ?-caprolactone. The dependence of the graft weight percentage on the reaction time was also studied. The graft copolymer is a compatibilizer for various polyethylene blends with engineering plastics. A functional polyethylene can be easily synthesized by the copolymerization of ethylene and 9-decen-l-ol using a homogeneous catalytic system of El(Ind)₂ZrCl₂/MAO. The resulting functional polyethylene was characterized by NMR, DSC, IR and TGA; and can also be utilized for grafting with ?-caprolactone. The grafted copolymer is also an effective compatibilizer.     

Crosslinking and characterization of commercially available poly(VDF-co-HFP) copolymers with 2,4,4-trimethyl-1,6-hexanediamine

Fluorinated copolymers are well known for their large range of applications. These applications can be improved by grafting or crosslinking of several agents. The mechanism of crosslinking of hexamethylene diamine and 2,4,4-trimethyl-1,6-hexanediamine is well known and occurs in four different steps. To elaborate a film of commercially available poly(VDF-co-HFP) copolymer crosslinked by 2,4,4-trimethyl-1,6-hexanediamine, a step of press cure under air is necessary. Temperature, time and pressure were optimised by regarding the solubility of the press cured films, the mechanical properties, the swelling rate in methyl ethyl ketone, and the degradation of the films. The best temperature, time and pressure for press cure were 150 °C, from 15 to 30 min, and 20 bars, respectively. Other properties of crosslinked poly(VDF-co-HFP) copolymers containing 10 mol.% and 20 mol.% of HFP were characterized. First, all films were insoluble in concentrated HCl. Secondly, swelling rates of different amounts of diamine crosslinked copolymers were measured in ethylene carbonate/dimethyl carbonate and in methyl ethyl ketone; it was proved that the higher the molar percentage of diamine, the higher the crosslinking density, so the lower the swelling rate. Concerning thermal properties, glass transition temperature mainly increased when the amount of diamine increased. Thermal stability measurements showed a higher decomposition temperature when the percentage of diamine was very low (5 mol.%). Finally, mechanical properties were measured by dynamic mechanical analysis; the storage tensile modulus (E′) of a diamine crosslinked Kynar^® copolymer versus temperature exhibited a high drop because Kynar^® was a highly amorphous copolymer. Moreover, the higher the amount of diamine, the higher the rubbery modulus.     

温敏性嵌段共聚物纳米胶束的制备及其稳定性

通过N-异丙基丙烯酰胺(NIPAAm)和N,N-二甲基丙烯酰胺(DMAAm)在链转移剂巯基乙醇存在下的自由基共聚,制备了具有端羟基的共聚物P(NIPAAm-co-DMAAm).利用其端羟基在异辛酸亚锡催化下引发己内酯开环聚合,得到了两亲性嵌段共聚物P(NIPAAm-co-DMAAm)-b-PCL,并在聚己内酯(PCL)链末端引入可光催化反应的不饱和双键.通过1H-NMR、GPC和相转变温度(LCST)等方法对聚合物进行了结构表征,测定了嵌段共聚物形成胶束的临界胶束浓度和胶束粒径,比较了核交联前后胶束的粒径和稳定性.结果表明:通过调节共聚物的组成,可获得LCST在40℃附近的胶束,胶束经核交联后,粒径有所减小,但稳定性明显提高,可用于对药物的温敏控制释放.     

Preparation of monodispersed vinylpyridine–divinylbenzene porous copolymer resins and their application to high-performance liquid chromatographic separation of aromatic amines

For the separation of aromatic amines, two types of monodispersed porous polymer resins were prepared by the copolymerization of 2-vinylpyridine and 4-vinylpyridine with divinylbenzene in the presence of template silica gel particles (particle size 5 μm), followed by dissolution of the template silica gel in an alkaline solution. The transmission electron micrographs and the scanning electron micrograph revealed that these templated polymer resins have a spherical morphology with a good monodispersity and porous structure. Using these monodispersed polymer resins, the high-performance liquid chromatographic separation of aromatic amines in the mobile phases of pHs 2.0, 2.9, 4.1, 7.2 and 11.7 were carried out. The 2-vinylpyridine–divinylbenzene copolymer resins showed slightly stronger retentions for aromatic amines than the 4-vinylpyridine–divinylbenzene copolymer resins. Under acidic conditions (around pH 2.0), aniline and the toluidines showed no retention on these copolymer resins due to the repulsion between the cationic forms of these amines and pyridinium cations in the stationary phase, whereas less basic aromatic amines or non-basic acetanilide showed slight retentions. Above pH 4.1, the separation of aromatic amines with these polymer resins showed a typical reversed-phase mode separation. Therefore, the separation patterns of aromatic amines are effectively tunable by changing the pH value of the mobile phases. A good separation of eight aromatic amines was achieved at pH 2.9 using the 2-vinylpyridine–divinylbenzene copolymer resins.     

STRUCTURAL CHARACTERIZATION OF POLY(ϵ-CAPROLACTONE) AND POLY(ϵ-CAPROLACTONE-b-ISOBUTYLENE-b-ϵ-CAPROLACTONE) BLOCK COPOLYMERS BY MALDI-TOF MASS SPECTROMETRY

Poly(?-caprolactone)(PC1) and PC1-polyisobutylene-PC1 (PC1-PIB-PC1) block copolymers were synthesized in anhydrous toluene by in situ conversion of 2-methyl-1-propanol (2M1P) and α,ω-dihydroxy PIB, respectively, to the corresponding aluminum alkoxide by reaction with a stoichiometric amount of triethylaluminum (TEA) followed by the addition of e-caprolactone. Structural characterization of 2M1P-initiated PCl by gel permeation chromatography (GPC) and matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry (MS) demonstrated the presence of cyclic oligomers, which are produced by intramolecular transesterification reactions that become significant at high monomer conversions. A minor fraction of chains bearing carboxylic acid termini was also observed in the MALDI-TOF mass spectrum; however, carboxylic acid chain ends could not be detected by ¹³C NMR analysis. Thus, the likely origin of the carboxylic acid termini is fragmentation of the initiator residue from the chain end during MALDI-TOF analysis. For PCl-PIB-PCl block copolymers, two different α,ω-telechelic PIB diols were used as macroinitiators, one derived from allyl and one from isopropenyl terminated PIB. Terminal olefins were converted to primary alcohols via regioselective hydroboration followed by alkaline hydrogen peroxide oxidation. After reaction with ?-caprolactone, formation of a block copolymer was evidenced by a shift of the polymer peak to lower elution volume in GPC analysis. Block copolymers possessed molecular weight distributions ≤1.4, and molecular weights of the PCl blocks calculated from GPC were in excellent agreement with those found using MALDI-TOF MS. Structural analysis indicated that the PCl end blocks were severed from the crude block copolymer during MS analysis, for both allyl- and isopropenyl-derived materials. For allyl-derived materials the PCl blocks were found to predominantly carry a C₂ residue at the point of detachment of the PIB block; however, the isopropenyl-derived block copolymers showed a complex mixture of different residues suggesting a complex fragmentation mechanism during loss of the PIB block.     

Advanced analytical methods for the structure elucidation of polystyrene-b-poly(n-butyl acrylate) block copolymers prepared by reverse iodine transfer polymerisation

Reverse iodine transfer polymerisation (RITP) is a living radical polymerisation technique that has shown to be feasible in synthesising segmented styrene-acrylate copolymers. Polymers synthesised via RITP are typically only described regarding their bulk properties using nuclear magnetic resonance spectroscopy and size exclusion chromatography. To fully understand the complex composition of the polymerisation products and the RITP reaction mechanism, however, it is necessary to use a combination of advanced analytical methods. In the present RITP procedure, polystyrene was synthesised first and then used as a macroinitiator to synthesise polystyrene-block-poly(n-butyl acrylate) (PS-b-PBA) block copolymers. For the first time, these PS-b-PBA block copolymers were analysed by a combination of SEC, in situ¹H NMR and HPLC. ¹H NMR was used to determine the copolymer composition and the end group functionality of the samples, while SEC and HPLC were used to confirm the formation of block copolymers. Detailed information on the living character of the RITP process was obtained.     

Novel perfluoropolyethers containing 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole blocks: synthesis and characterization

Peroxidic perfluoropolyethers (PFPEs) are industrial intermediates used by Solvay Solexis for the preparation of different classes of (per)fluoropolyethers (Fomblin^®, Galden^®, Solvera^®, Fluorolink^®). The chemistry of these peroxidic compounds has been recently exploited for the synthesis of novel PFPE block copolymers. In the present work we report the synthesis, the structural and physical-chemical characterization of block copolymers obtained by the reaction of peroxidic PFPEs with 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, a cyclic homopolymerizable perfluoroolefin. These block copolymers combine the most attractive properties of the PFPEs, like the excellent lubrication, the high thermal stability and the optical transparency, with new specific properties which are related to the perfluorodioxolenic blocks.     

聚环氧乙烷-g-聚己内酯两亲性接枝共聚物的合成及药物释放行为

通过环氧丙醇(GL)与环氧乙烷(EO)的阴离子顺序开环聚合制备了水溶性嵌段共聚物PEO-b-PGL, 以PGL嵌段每个重复单元的侧羟基为引发点进一步引发ε-己内酯(CL)的开环聚合, 合成了结构规整的以聚环氧乙烷(PEO)为主链的两亲性接枝共聚物(PEO-b-PGL-g-PCL). 研究了PEO-b-PGL-g-PCL在水相中的自组装行为, 采用稳态荧光探针法测定了胶束的临界胶束浓度(cmc). 以疏水性药物阿霉素(DOX)为模型药物, 研究了两亲性接枝共聚物的化学组成对药物的扩散释放以及降解释放行为的影响.