5-溴-3-叔丁基水杨醛的合成

以2-叔丁基苯酚、镁和多聚甲醛为原料,甲醇为溶剂,经甲酰化反应合成了3-叔丁基水杨醛,再经溴化反应合成了5-溴-3-叔丁基水杨醛.考察了溶剂、反应温度、物料比等对产品收率的影响.5-溴-3-叔丁基水杨醛合成的较优条件为:n(3-叔丁基水杨醛)∶n(液溴)=1∶1.1,反应溶剂为乙醇,反应温度60℃,反应时间8 h,产品经1H-NMR表征确认.     

聚[3-(6-溴己基)噻吩]的合成与表征

以3-溴噻吩、正丁基锂和1,6-二溴己烷为原料,经过改良的Li-Br交换反应、溴化反应、GRIM法成功合成了聚[3-(6-溴己基)噻吩]。通过傅里叶变换红外光谱(FT-IR),核磁共振波谱(1 H-NMR)、GPC、紫外吸收分光光谱(UV-Vis)及荧光发射光谱(PL)对中间产物及聚合物进行了结构和性能表征。结果表明,所合成聚合物与目标产物的结构一致。聚合物的数均分子量为5725,多分散系数为1.39,在氯仿溶液中最大吸收波长在398nm,最大发射波长在553nm。     

氢键交联聚异丁烯网络制备

以3-氨基-5-乙酰胺-1,2,4-三氮唑(AATA)在相转移催化剂存在的条件下取代溴化异丁烯-对甲基苯乙烯共聚物弹性体(BI MS)中的溴原子,在高分子链上引入3-氨基-5-乙酰胺-1,2,4-三氮唑(AATA),利用其分子间的氢键自组装形成聚异丁烯网络。BI MS反应后溶液的比浓黏度增加,以及比浓黏度随着BI MS中AATA量的增加而急剧增加表明体系中形成了网络。文中还研究了反应时间、温度、AATA用量对反应的影响。结果表明,AATA在两相催化剂存在的条件下可以取代BI MS中的Br,但不能完全取代。当反应温度在75℃左右,AATA/Br为4/1(mol/mol),反应时间不超过8 h时,溴的取代率可以达到30%以上。     

α,α’，2，3，5，6-六溴对二甲苯合成研究

摘要：本文报道了新型溴系阻燃剂α,α‘，2，3，5，6-六溴对二甲苯的合成方法。首次一步法合成了α,α‘，2，3，5，6-六溴对二甲苯，即由对二甲苯经催化溴化制得2，3，5，6-四溴对二甲苯，不经分离直接在引发剂催化下进行α-位甲基溴化，合成α,α‘，2，3，5，6-六溴对二甲苯。第一步反应的催化剂三氯化铝对第二步自由基取代反应具有较大影响，在亲电取代反应结束后必需加入一定量的甲醇破坏三氯化铝，否则不能得到预期的产物。     

PPO/SiO_2碱性阴离子交换膜的制备与表征

本研究是基于聚(2,6-二甲基-1,4-苯撑氧)(PPO)所进行的系列改性工作.PPO进行溴化,得到两种溴化度的溴化PPO(BPPO),再进行羟基化和季铵化反应,随后与小分子烷氧基硅烷进行sol-gel反应,热处理后将膜浸泡在碱液中转化为OH-型,得到两种系列的碱性阴离子交换膜.膜具有平整均一的外观形貌和良好的机械性能(4.5~12 MPa,36%~58%),膜的厚度范围为0.09~0.12 mm.水含量(WROH)范围为62%~145%,离子交换容量为1.6~2.2 mmol/g.膜具有良好的抗碱能力,在2 mol/L NaOH中浸泡192 h后,其IEC仍能保持在原有的82%以上.低溴化度BPPO制备的膜具有更高的抗溶胀能力,在60℃水中浸泡44 h后,溶胀度范围为117%~297%,高溴化度BPPO制备的膜有高的电导率(室温条件下为0.036~0.041 S/cm),说明所制备的碱性阴离子交换膜有潜力应用于碱性膜燃料电池领域.     

溴化环氧化天然橡胶的制备与表征

采用胶乳法对天然橡胶(NR)进行环氧化和溴化制备溴化环氧化天然橡胶(BENR),考察溴化工艺如溴化时间、溴化温度、体系pH和溴化剂用量对BENR溴含量和羟基含量的影响,并采用傅里叶变换红外光谱、核磁共振光谱和热重分析对BENR产物的微观结构进行表征。结果表明,环氧化天然橡胶(ENR)在溴化反应中发生了α-取代反应,另外环氧基团还发生开环反应生成了羟基;BENR在N_2中分3个阶段降解,在空气中分4个阶段降解;溴化剂用量为10 mL,溴化时间为20 min,溴化温度45℃,体系pH值为2时,BENR溴含量和羟基含量分别为44.89%和1.59%,随着溴含量的增加,BENR逐渐失去弹性变为粉末状。     

1-己基-3-甲基咪唑六氟磷酸盐离子液体的微波辅助合成与结构表征

采用1-溴代己烷和N-甲基咪唑为原料,微波辅助快速合成了溴化1-己基-3-甲基咪唑([HMIM]Br)中间体,此步反应产率可达到95%。通过将中间体和六氟磷酸钾进行离子交换,制备了离子液体1-己基-3-甲基咪唑六氟磷酸盐([HMIM]PF6),产率约为48%。与传统方法相比,反应时间极大地缩短。产物的结构经傅立叶变换红外光谱(FT-IR)、超导脉冲傅立叶变换核磁共振氢谱(1HNMR)和超导脉冲傅立叶变换核磁共振碳谱(13CNMR)确认,纯度经高效液相色谱法(HPLC)分析达到99.0%以上。     

具有支化结构溴化丁基橡胶的合成及表征

研究了将锂端基苯乙烯-异戊二烯共聚物溶液与溴化丁基橡胶胶液反应合成具有支化结构的溴化丁基橡胶的方法,以期提高丁基橡胶的某些性能,拓宽丁基橡胶的应用领域.采用三台联用(LS VIS RI)、DSC、氧弹燃烧等方法对合成产物进行表征,并将产物硫化测定其硬度、拉伸应力、比重等性能,与非支化溴化丁基橡胶之性能进行对比.     

纳米铜/PMMA-b-PS的超声合成及有序组装

在超声辐射作用下,以α-溴代丙酸乙酯为引发剂,溴化亚铜/2,2-联吡啶为催化体系,通过原子转移自由基聚合(A-TRP)制备了分子链末端含有一个α-溴原子的聚甲基丙烯酸甲酯(PMMA-Br)。以此为大分子引发剂引发苯乙烯单体进行ATRP反应,制得聚甲基丙烯酸甲酯嵌段聚苯乙烯(PMMA-b-PS)共聚物。通过硼氢化钠还原聚合物体系中的溴化亚铜,从而得到纳米铜/PMMA-b-PS复合粒子。红外光谱(FT-IR)和核磁共振(1H-NMR)表征嵌段共聚物的结构;凝胶渗透色谱(GPC)测定了共聚物的相对分子量和多分散系数;X射线光电子能谱(XPS)证明纳米铜和PMMA-b-PS嵌段共聚物中PMMA之间存在一定的相互作用;通过高分辨透射电子显微镜(HTEM)观察到纳米铜具有诱导聚合物组装的现象。     

溴化丁基橡胶的结构研究进展

介绍了溴化丁基橡胶中不同的溴化结构形式,包括没有参与溴化反应的结构Ⅰ,以及溴化结构Ⅱ(Exomethyl Structure)和结构Ⅲ(Rearrange Structure)。其中,结构Ⅲ是结构Ⅱ的重排结构。这两种溴化结构在发生脱卤反应时会得到两种共轭双键结构,分别为结构Ⅳ(Exo-conjugated Diene)和结构Ⅴ(Endo-conjugated Diene)。着重对溴化丁基橡胶中的溴化结构对性能的影响进行了系统阐述,为提高溴化丁基橡胶的性能提供了借鉴与参考。     

Refractive indices and extinction coefficients of polymers for the mid-infrared region

Refractive indices and extinction coefficients of several polymers have been measured for the wide infrared wavelength region. The polymers used as coating materials have also been found useful for low-loss hollow waveguides for the transmission of Er:YAG, CO, and CO(2) laser light, respectively.     

Piezoelectric composites of PZT and some semi-crystalline polymers

Piezoelectric composites of PZT ceramics and several semi-crystalline polymers have been produced by embedding slender PZT rods (4 volume percent) in the polymers. The observed dielectric constants were considerably lower than that of pure PZT. The hydrostatic piezoelectric voltage coefficients of the composites were larger than PZT, even though the composite hydrostatic piezoelectric strain coefficients were lower. Composite figures of merit ranged from one-third to six times that of PZT.     

Modeling the hygroexpansion of aligned wood fiber composites

The effect of wood fiber ultrastructure and cell wall hygroelastic properties on wood fiber composite hygroexpansion has been analyzed. An analytical concentric cylinder model extended to include also free hygroexpansion of orthotropic phase materials has been used on several length scales. Using properties of the three main wood polymers, cellulose, hemicellulose and lignin the longitudinal and transverse hygroexpansion coefficients for the microfibril unit cell were obtained and the volume fraction change of the wood polymers in the microfibril unit cell depending on relative humidity was calculated. The fiber cell wall was modeled regarding each individual S1, S2 and S3 layer and the cell wall longitudinal hygroexpansion coefficient was determined depending on microfibril angle in the S2 layer. A homogenization procedure replacing the S1, S2 and S3 layers with one single layer was found not to influence the results significantly for low microfibril angles. Finally the hygroexpansion coefficients of an aligned softwood fiber composite were calculated.     

Molecular level investigation into selective permeability of silicon based membranes with potential use in gas separation processes

Abstract

The effect of the modification of the molecular structure on the permeability coefficients of typical rubbery and glassy silane and siloxane polymers at different temperatures was experimentally investigated. It was shown that carbon dioxide had higher permeability coefficients than those of nitrogen and oxygen due to the higher affinity of the various polymers toward the gas molecules. In order to provide a detailed understanding into the effect of the molecular structure on the gas diffusion behaviour in polymers, molecular modelling of carbon dioxide diffusion in silicon based membranes was used. The polymer molecules were shown to have lower self-diffusion coefficients than the gas ones related to the small size of the gas molecules as compared to the large size of the polymeric segments, thus allowing the gas molecules to jump from one unoccupied site to another through a series of connected pores or channels within the polymeric matrix. Increasing the temperature was shown to have a proportional effect on the mean square displacement, possibly due to the increase in the kinetic energy available to the systems. At high temperatures, the glassy siloxane molecules had similar values for the mean square displacement to those of the gas molecules since the polymer in this case is in close proximity to its glass transition temperature. The presence of the alternating oxygen atoms in the main backbone of the polymeric chains led to higher values for the selfdiffusion coefficients for the siloxane polymers as compared to those of the silane polymers as a result of the change in the bond angle about the oxygen atom (~ 144°) as compared to the tetrahedral angle (~ 110°) about the silicon atoms.     

Novel promising crosslinkable tricyanopyrroline polymeric electro-optic materials

A tricyanopyrroline chromophore with methacrylate reactive group was synthesized to fabricate the side chain (polymer 1) and crosslinkable (polymer 2) EO (electro optic) polymers with enhanced electrooptical tensor coefficients. These type of polymers have demonstrated the large EO coefficients with values of 29 pm/V and 25 pm/V at wavelength 1,310 nm, respectively. Compared with polymer 1, t polymer 2 had demonstrated a better stability of polar structure. The thermal stability of polar structure was improved for about 100 °C. The temperatures of poling and crosslinking processes were compatible in polymer 2, which allowed obtaining the EO films with improved features. The experimental results have been interpreted with the aid of quantum-chemical calculations.     

Effect of electron donor/acceptor substituents on the Seebeck coefficient and thermoelectric properties of poly(3-methylthiophene methine)s/graphite composites

Recently, the use of polymers as thermoelectric materials has attracted considerable attention. However, relatively few studies have investigated the effects of polymer structures on the corresponding thermoelectric properties of the polymers. In this work, a series of poly(3-methylthiophene methine)s (PMMs) were synthesized for use as thermoelectric materials, and the effects on the Seebeck coefficient of donor or acceptor side groups at the methine carbon were studied. The PMMs with strongly electron-withdrawing and electron-donating groups exhibited the highest Seebeck coefficients. Motivated by the high Seebeck coefficients of the selected PMMs, PMM/graphite composites were prepared via solution mixing followed by mechanical ball milling and cold pressing. The thermoelectric properties of the composites were investigated as a function of the graphite (G) concentration. The highest ZT (6.23 × 10⁻³) was measured for the poly[(3-methylthiophene-2,5-diyl) (p-(methoxy)benzylidene)]/G composite that contained 90 wt% G. The results of this work suggest that the thermoelectric properties of polymer-inorganic composites can be improved by designing polymers with high Seebeck coefficients.     

Diffusion coefficients of water and leachables in methacrylate-based crosslinked polymers using absorption experiments

The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10⁻⁸ cm²/sec (co-monomer TMTMA) to 3.15 × 10⁻⁸ cm²/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R ² = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R ² = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure.     

Utilization of the thermal strain of solids for determining the constants of internal heat transfer of solid-phase polymers

The article describes a rapid dilatometric method, absolute in instrumental provisions of determining the heat-transfer coefficients, thermal diffusivity, coefficients of thermal expansion and of volumetric heat capacity of polymers.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 1, pp. 80–86, January, 1985.     

Quartz crystal microbalance sensor for organic vapor detection based on molecularly imprinted polymers

Molecularly imprinted polymers on quartz crystal microbalances (QCM) are examined for their ability to detect vapors of small organic molecules with greater sensitivity and selectivity than the traditional amorphous polymer coatings. Hydroquinone and phenol serve as noncovalently bound templates that generate shape-selective cavities in a poly(acrylic) or poly(methacrylic) polymer matrix. The imprinted polymers are immobilized on the piezoelectric crystal surface via a precoated poly(isobutylene) layer. The behavior of the imprinted polymer films is characterized by the dynamic and steady-state response of the QCM frequency to pulses of organic vapors in dry air. The apparent partition coefficients are determined for imprinted and nonimprinted polymers prepared by two synthetic methods and for varying mole ratios of template to monomer. The hydroquinone-imprinted polymers and, to a lesser extent, the phenol-imprinted polymers exhibit greater sensitivity and higher selectivity than the nonimprinted polymers toward organic vapors that are structurally related to the templates. These results indicate that molecularly imprinted polymers are promising for the development of selective piezoelectric sensors for organic vapor detection.     

Tribological properties of polymers PI,PTFE and PEEK at cryogenic temperature in vacuum

The effects of temperature, sliding speed and load on the tribological properties of polyimide (PI), polytetrafluoroethylene (PTFE) and polyetheretherketone (PEEK) at cryogenic temperature in vacuum were investigated using a ball-on-disk tribometer. At cryogenic temperature, polymers show higher hardness which results in decreasing contact area between the friction pairs. Moreover, the real surface area in contact between steel ball and polymer disk determines the friction coefficient instead of the formation and adhesion of the transfer film. Thus, the friction coefficients at cryogenic temperatures are lower than at room temperature. On the other hand, wear rates of the three polymers decrease as temperature decreases since molecular mobility and migration are limited at cryogenic temperatures. For the visco-elasticity of PI, PTFE and PEEK, the friction coefficients fall as the load increases.