Properties and influence of hydrophobically associating polyacrylamide modified with 2-phenoxylethylacrylate

The properties of hydrophobically associating copolymer P(acrylamide (AM)/2-phenoxylethylacrylate (POEA)), composed of acrylamide and a small amount of POEA (⩽1.0 mol.%) as hydrophobe, were investigated in aqueous solution under various conditions. The results showed that the solution properties were strongly affected by the microstructure of copolymer. The copolymers (BP series) with hydrophobic microblocky structure exhibited large viscosity enhancement due to the intermolecular hydrophobic association, while that did not occur for the random copolymers (RP series). The hydrophobic association thickening behaviors were also remarkably dependent on the number and length of the hydrophobic block in polymer chain. Nonlinear viscosity relationship was found as increasing hydrophobe content and SMR (surfactant/hydrophobic monomer molar ratio), and a maximum appeared at the middle position as a result of the competitive effect between inter- and intra- molecular hydrophobic associations. Solution properties were further studied as a function of the polymer concentration, salinity, temperature and shear rate. The block copolymers show high salt tolerance and shear thinning as well as recovery after shear.     

Synthesis and characterization of novel triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(γ-benzyl L-glutamate)s as outer blocks

Background Bioactive and biodegradable polyurethanes (BDPUs) have drawn much attention in recent years. As part of the research program to search for novel prepolymers for BDPUs, a study was carried out on the synthesis and characterization of triblock copolymers comprising poly(tetrahydrofuran) as a central block and poly(γ-benzyl L-glutamate)s as outer blocks. Results A new macroinitiator terminated with phenylalanine was first prepared from the condensation of a distal hydroxy poly(tetrahydrofuran) with N-tert-butoxycarbonyl L-phenylalanine in the presence of dicyclohexylcarbodiimide, followed by removing the protecting group. Then, it was employed to initiate the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride in varying feeding ratios to give rise to the targeted triblock copolymers. Conclusions The length of the outer poly(γ-benzyl L-glutamate) blocks was well tailored by varying the monomers to macroinitiator feeding ratio. All the triblock copolymers exhibited a nearly symmetrical and unimodal molecular weight distribution while only one distinct glass transition temperature was evidenced from −10°C to 25°C.     

Surface‐Shielding Nanostructures Derived from Self‐Assembled Block Copolymers Enable Reliable Plasma Doping for Few‐Layer Transition Metal Dichalcogenides

Precise modulation of electrical and optical properties of 2D transition metal dichalcogenides (TMDs) is required for their application to high‐performance devices. Although conventional plasma‐based doping methods have provided excellent controllability and reproducibility for bulk or relatively thick TMDs, the application of plasma doping for ultrathin few‐layer TMDs has been hindered by serious degradation of their properties. Herein, a reliable and universal doping route is reported for few‐layer TMDs by employing surface‐shielding nanostructures during a plasma‐doping process. It is shown that the surface‐protection oxidized polydimethylsiloxane nanostructures obtained from the sub‐20 nm self‐assembly of Si‐containing block copolymers can preserve the integrity of 2D TMDs and maintain high mobility while affording extensive control over the doping level. For example, the self‐assembled nanostructures form periodically arranged plasma‐blocking and plasma‐accepting nanoscale regions for realizing modulated plasma doping on few‐layer MoS₂, controlling the n‐doping level of few‐layer MoS₂ from 1.9 × 10¹¹ cm^?2 to 8.1 × 10¹¹ cm^?2 via the local generation of extra sulfur vacancies without compromising the carrier mobility.     

TAIC对辐照交联无卤阻燃EVA热缩材料的影响

向乙烯-醋酸乙烯共聚物(Ethylene-vinyl acetate copolymer,EVA)无卤阻燃热缩材料中添加不同含量的三烯丙基异氰脲酸酯(Triallyl isocyanurate,TAIC),然后采用电子束辐照,制备出交联型无卤阻燃EVA热缩材料。考察TAIC的含量和吸收剂量对样品的凝胶含量、机械性能和电性能的影响,并通过傅里叶红外(Fourier transform infrared,FTIR)光谱对EVA热缩材料进行表征。结果表明:TAIC的加入对辐射交联有促进作用,在吸收剂量一定的情况下,如150 k Gy,EVA热缩材料的凝胶含量随着TAIC含量增加;在TAIC的添加量一定的情况下,如3份(质量),EVA热缩材料的凝胶含量随着吸收剂量增加;对机械性能而言,断裂伸长率随着TAIC和吸收剂量的增加均呈下降趋势;在断裂强度方面,添加TAIC的样品断裂强度上升趋势比较明显;对电性能的影响,TAIC的加入增加了EVA热缩材料的体积电阻,其随着吸收剂量的增加先上升后下低;FTIR分析表明TAIC在电子束辐照下反应完全。     

Synthesis and properties of a poly(sodium acrylate) bioadhesive nanocomposite

Poly(sodium acrylate) (PNaA) based nanocomposites were synthesized using different nanosilver loadings via redox solution polymerization at room temperature and under full exposure to the atmosphere. The nanocomposites exhibited increasing antibacterial activity with increased nanosilver content. Biocompatibility was determined using an MTT assay; no significant cytotoxicity was observed at the examined nanosilver loadings. Adhesion was measured using a tensile test and the stress versus strain curve showed an acceptable stress development in the model tissue using bioadhesive containing 2 wt% nanosilver. Introducing a second, more degradable polymer to the system as an interpenetrating polymer network enabled tuning the bioadhesive degradation rate.     

无磷水基金属清洗剂的研制

研究了阴/阳离子表面活性剂的复配及该体系在水基金属清洗剂中的应用,比较了马来酸酐-丙烯酸共聚物的钠盐、三聚磷酸钠与4A沸石的助洗性能.并通过试验确定了金属清洗剂的配方:AESA(C12脂肪醇聚氧乙烯醚硫酸铵):BJH-1(脂肪胺类,自制):OP-10(辛基酚聚氧乙烯醚):M550(卤化二甲基二丙基铵丙酰铵共聚物)=6∶4∶4∶1(摩尔比),并将其按质量比95∶5加入Na-CP4(马来酸酐及丙烯酸共聚物的钠盐)及硅酸钠做助洗剂,对其5%稀释液的洗涤效果和防锈性能进行了评价.结果表明,该清洗剂具有较强的去污能力和良好的防锈性能,不含磷化物,对环境友好.     

APPLICATIONS OF COMPOSITION CONTROL TO THE STYRENE-BUTYL ACRYLATE EMULSION COPOLYMERIZATION

Three different operating modes to produce constant composition copolymers in emulsion are examined. Experimental data are presented with reference to the binary copolymerization of styrene and butyl acrylate. Firstly, combining a composition-conversion model with the on-line monitoring of conversion through densimetry, a semibatch monomer feed policy aimed to minimize the reaction time is discussed. Secondly, a batch, pseudo-azeotropic mode is analyzed. A constant composition polymer is obtained by properly adjusting the initial amount of water to take advantage of the different monomer solubilities in aqueous phase. Finally, a semibatch case is examined where limitations of maximum reaction rate are operative. Once more, the composition-conversion model is combined with a suitable on-line monitoring of conversion by measurements of the ultrasound velocity in the reacting system.     

SBS和MMA—丙烯酸丁酯接枝聚合物的溶解性和溶度参数的订定

研究了接枝最为２１．９２％的接枝聚合物ＳＢＳ－ｇ－Ｐ（ＭＭＡ－ＢＡ）在４１种溶剂中的溶解性,表明该聚合物能完全溶解在氯仿、四氯化碳、苯、甲苯、乙酸乙酯、二氧化己环等溶剂中。用浊度滴定法测定该接枝聚合物的溶度参数为９．０３（ｃａｌ／ｃｍ＾３）＾１／２,用特性粘数法测定的溶度参数为９．００（ｃａｌ／ｃｍ＾３）＾１／２。     

聚丙烯酸酯—聚有机硅氧烷复合乳液的合成与性能

以在丙烯酸甲酯、丙烯酸丁酯、甲基丙烯酸、八甲基环四硅氧烷（Ｄ４）和乙基七甲基环四硅氧烷（ＶＤ４）为共聚单体,在８５℃下采用一次投料合成了稳定的聚丙烯酸酯－聚有机硅氧迷雾复合乳液。实验结果表明,当ＶＤ４／Ｄ４摩尔比为０．００８,有机硅质量分类小于２０％时,单体转化率均高于８２％,胶乳粒径为５０－６０ｎｍ,且粒径分布均匀;当有机硅质量分数大于２５％时,聚合过程中有凝聚物产生,乳液不稳定,胶膜的拉伸强度     

不饱和聚酯和环氧树脂嵌段共聚物的研究

本文利用环氧基功能团与羟基反应,使聚酯分子扩链,合成了A—B—A型嵌段共取物,其耐酸碱性比普通型不饱和聚酯强可与3301双酚A型不饱和聚酯媲美,提高了聚酯的耐碱性。