EPR-g-PS接枝共聚物的大分子单体共聚物合成及表征

将阴离子聚合所得末端带有烯丙基的窄分布聚苯乙烯大分子单体(PSallyl)与乙烯、丙烯在钒催化体系下进行共聚合,得到聚苯乙烯(PS)支链沿乙丙橡胶(EPR)主干无规分布的接枝共聚物EPR-g-PS。接枝效率为70％左右。大分子单体的分子量、加入量,催化剂浓度和聚合温度等对共聚反应及其产物结构有明显的影响。丁酮为选择沉淀剂可分离未反应的聚苯乙烯大分子单体。用紫外光谱、核磁共振、渗透压和凝胶渗透色谱法测定了纯制接枝共聚物的组成和分子量。结果表明所合成的EPR-g-PS的聚苯乙烯含量为5—45％;支链为分子量1.0—7.8×10~4的窄分布((?)=1.05—1.17)聚苯乙烯;平均支链数为1—4。     

EPR-g-PS热塑弹性体的形态结构

电子显微镜观察表明,以乙丙橡胶(EPR)为主干,聚苯乙烯(PS)为支链的接枝共聚物EPR-g-PS的基本形态是高度分散的聚苯乙烯微区(约几百?)存在于乙丙橡胶连续相中的两相体系,随接枝共聚物中聚苯乙烯含量增加,微区形态发生变化,少量的接枝共聚物在PS与EPR共混物中起“增容剂”作用,使分散相微区变得小而均匀,多重玻璃化转变的存在进一步证实了接枝共聚物相分离的形态结构。     

接枝共聚物EPR-g-PS作PS/EPDM共混体系增容剂的探讨

使用了由大分子单体共聚合制备的以乙丙橡胶(EPR)为主干、聚苯乙烯(PS)为支链的接枝共聚物EPR-g-PS作为PS/EPDM共混体系的增容剂。实验结果表明,共混体系的组成、增容剂加入量以及增容剂分子结构对共混体系冲击强度有很大影响。将这些因素与相差显微镜及扫描电镜研究所揭示的共混物形态的变化相联系,对此类接校共聚物作为不相容体系增容剂的机理作了探讨。     

降冰片烯端基聚苯乙烯大分子单体的合成

近年来,大分子单体的合成及其共(自)聚合正日渐成为高分子合成中非常活跃的领域。本试验室曾合成了具有烯丙基端基的聚苯乙烯大分子单体(PS-allyl),并将其与乙烯、丙烯共聚合得到了乙丙共聚物(EPR)为主干、聚苯乙烯(PS)为支链的接校共聚物EPR-g-PS。本工作以5-溴甲基-2-降冰片烯(BrMNB)与聚苯乙烯阴离子(PS^-)偶合,制备具有降冰片烯端基的聚苯乙烯大分子单体(PS-NB)。     

降冰片烯封端的聚苯乙烯大分子单体与乙烯共聚的初步报告

大分子单体(macromer)共聚合为合成结构确定的接枝共聚物提供了新途径,但用络合催化剂进行共聚的例子很少。前文报导了末端为降冰片烯(NB)的聚苯乙烯大分子单体PS-NB的合成及表征;现报告其与乙烯的共聚,以制备主干为聚乙烯(PE)、支链为聚苯乙烯(PS)的接枝共聚物PE-g-PS的初步结果。     

聚苯乙烯大单体与丙烯酸酯接枝共聚物对聚苯乙烯表面的改性研究

研究了由大单体技术合成的侧链为聚苯乙烯、骨架由丙烯酸丁酯或甲基丙烯酸羟乙酯/丙烯酸丁酯组成的接枝共聚物对聚苯乙烯的表面改性效果(试样浇注于玻璃纸上成膜)。发现仅添加0.5wt％的接枝共聚物就可完全改变聚苯乙烯膜两面的临界表面张力γ-c与表面能中的色散力部份γ_s~D,少量添加的接枝共聚物在改性聚苯乙烯膜的两面呈现出明显的表面富集现象。虽然两类接枝共聚物的极性有较大的差异,但改性聚苯乙烯成膜后的自由表面均显示出与聚丙烯酸丁酯相同的低表面能(γ_s~D=37×10~(-3)牛顿·米~(-1)),而添加三元接枝共聚物的改性膜与玻璃纸接触的表面却具有高于聚苯乙烯的表面能|(γ_s~D=54×10(-3)牛顿·米~(-1))。这种改性膜的两面具有不同的表面能是由于接枝共聚物中不同的组分在膜的两面富集所致,已通过ESCA的表面测试结果证实,并与按Gibbs吸附式的计算值相符。     

嵌段-接枝共聚物SEPG与PS(OH)之间的氢键络合导致胶束化的研究

利用原子转移自由基聚合反应合成了以聚苯乙烯-b-聚(乙烯-co-丙烯)(SEP)为主链、无规分布且数目可控的聚甲基丙烯酸乙酯(PEMA)为支链的嵌段接枝共聚物SEPG.发现在甲苯中因支链PEMA与聚(苯乙烯-co-对六氟羟丙基-α-甲基苯乙烯)[简称PS(OH]的氢键络合作用和EP嵌段的溶解作用导致了聚集体的胶束化.研究了胶束的尺寸及其分布对PS(OH)中羟基含量和共混物组成的依赖性.     

HIPS／SBS共混物的形态结构和性能

通常,高抗冲聚苯乙烯(HIPS)为多相体系,由连续聚苯乙烯(PS)相和分散的聚丁二烯(PB)颗粒组成。PB含量一般为5～15%,粒径范围为0.5～10μm,PB颗粒是交联的,同时含有接枝的PS,其内部结构由制备工艺决定。HIPS力学性能与其制备工艺、PB含量、PB分子结构、相区尺寸及内部结构密切相关。PS和PB嵌段共聚物(SBS)通常为热塑弹性体,由于PS段和PB段的不相容性而呈现微相分离的结构特征。SBS常用于与其它聚合物共混以增加后者的韧性。本工作研究了HIPS/SBS共混物的形态结构和力学性能。     

通过原子转移自由基聚合合成可光交联的聚苯乙烯接枝共聚物

聚苯乙烯(PS)在氯化锌(ZnCl_2)做催化剂下,通过氯甲基甲基醚氯甲基化反应,合成了氯甲基化聚苯乙烯(CMPS).在氯化亚铜/联二吡啶(CuCl/bpy)催化下,以CMPS为大分子引发剂引发甲基丙烯酸甲酯(MMA)、甲基丙烯酸酯化查尔酮(MSPK)进行原子转移自由基聚合,成功合成了侧链含有查尔酮结构的光敏聚苯乙烯接枝共聚物(PSMM),所得聚合物结构经过红外光谱(FT-IR)、核磁共振氢谱(~1H NMR)得到确认,通过热重分析(TG)、示差扫描量热法(DSC)测试了该聚合物的热学性能.结果表明,该接枝共聚物具有较好的热学性能及良好的光敏性.     

活性正离子聚合及原位制备聚醋酸乙烯酯-g-聚四氢呋喃共聚物/纳米银复合材料

通过将烯丙基溴/高氯酸银引发体系引发四氢呋喃活性正离子开环聚合与"grafting onto"合成方法相结合,原位制备了不同接枝密度和接枝链长度的新型聚醋酸乙烯酯-g-聚四氢呋喃接枝共聚物(PVAc-g-PTHF)及其与纳米银(Ag)的复合材料.采用傅里叶变换红外光谱(FTIR)、核磁共振波谱(1H-NMR)和多角度激光光散射-黏度-凝胶渗透色谱仪(MALLS-VIS-GPC)分别表征了该接枝共聚物的化学结构、共聚组成、分子量、分子量分布、接枝支链数目及支化度,采用原子力显微镜(AFM)、示差扫描量热分析(DSC)、偏光显微镜(POM)研究了接枝共聚物中接枝支链数目及支链长度对其微观形态、单端受限链段结晶行为的影响,并探讨了该纳米复合材料的抗菌性能.结果表明:所制备的不同支链数目和支链长度的PVAc-g-PTHF/Ag纳米复合材料,均表现出良好的抗菌性能;接枝共聚物PVAc-g-PTHF的重均分子量可达4.52×10~5,分子分子量较窄(M_w/M_n~1.8),支化因子可达0.19.接枝共聚物PVAc-g-PTHF可形成明显的相分离结构,其微观形态与接枝支链数目有关;相比相同分子量的双端不受限的PTHF链,PVAc-g-PTHF接枝共聚物中单端受限PTHF支链的结晶速率明显降低;在确定接枝支链数目的情况下,随着支链中PTHF链段长度增加,其结晶逐渐增强,结晶熔融温度及熔融焓均稍有增加.     

硅氢加成型室温固化硅橡胶胶粘剂的研究

<正> 我们研制了一种硅氢加成型室温固化硅橡胶,这种橡胶不但有较好的力学性能,而且与各类材料如金属、塑料、陶瓷、玻璃等都有很好的粘结力,是一种具有弹性的胶粘剂。该胶粘剂是利用一种含乙烯基聚硅氧烷、含氢聚硅氧烷以及二氧化硅补强剂在铂催化剂     

The effect of hard and soft segment composition and molecular architecture on the morphology and mechanical properties of polystyrene-polyisobutylene thermoplastic elastomeric block copolymers

This paper reports the effects of hard (polystyrene, PS) and soft (polyisobutylene, PIB) segment composition and the molecular architecture (linear versus star, PS and PIB block length) on the morphology and mechanical properties of polystyrene/polyisobutylene (SIBS) block copolymers synthesized by living carbocationic polymerization. Atomic force microscopy, dynamic mechanical thermal analysis and tensile testing verified the phase-separated nature of the block copolymers, which behaved as thermoplastic elastomers (TPEs). The morphology of these TPEs is similar to polydiene-based TPEs, and is defined by the soft/hard segment composition. Interestingly, topology (linear vs star) did not have a major influence on morphology. Tensile testing showed that for both linear and three-arm star block copolymers, the modulus and tensile strength increased while elongation at break decreased with higher PS content. However, three-arm star block copolymers showed larger moduli than their linear homologues with similar PS content and PIB arm length, indicating the influence of molecular architecture on mechanical properties. These results might serve as a foundation for macromolecular engineering design for optimizing properties.     

Mechanical properties and characteristic of surface treated bamboo fiber reinforced PP/PS blends

Bamboo fiber (BF) as organic filler is characterized by mechanical properties analysis and morphology examination for polypropylene (PP) and polystyrene (PS) matrix blends. Effects of different filler content on tensile strength, flexural properties, and impact strength are proposed. It is observed from scanning electron microscopy (SEM) studies that addition of BF is beneficial in increasing mechanical strength via increasing the interface dispersed phase. The optimum tensile properties and impact properties of BF content were at 40 wt% for PP/PS/BF composite on melt mixing conditions. The results showed a significant improvement in mechanical properties of PP/PS/BF ternary blend composite. Comparing with untreated BF, content of carbon and nitrogen of treated BF decreased to 66.57 and 2.31%, oxygen content increased to 21.07%, and silicon content increased from 0 to 10.04%. The element ratio of O/C, N/C, and Si/C changed to 31.65, 3.47, and 15.08, respectively.     

Poly(ethylene-co-propylene)-g-polystyrene through macromer polymerization: Preparation,morphology, and structure–properties relationships

Graft copolymers with ethylene-propylene (EPR) backbone and polystyrene (PS) grafts, EPR-g-PS, were prepared by terpolymerization of a PS macromer with ethylene and propylene using a vanadium catalyst, with graft efficiency of up to 80% and PS content in the copolymer 5–45%. Such polymerization parameters as molecular weight and dosage of the macromer, catalyst concentration, and reaction temperature which affect the mobility and hence polymerizability of the macromer may have a marked influence on the polymerization and the structure of the products. The molecular architecture of the copolymers was characterized by osmometry, UV, NMR, and GPC methods. TEM and torsional pendulum studies revealed that EPR-g-PS possessed a phase separation morphology with PS domains evenly dispersed in the EPR matrix. The PS content and average number of grafts strongly influence the tensile properties of the copolymers. EPR-g-PS graft copolymers prepared by macromer copolymerization exhibit the mechanical properties of a typical thermoplastic elastomer having two or more branches of a certain length.     

Mechanics of polymer nanocomposites modified with fulleroid nanofillers

Polymer nacomposites based on thermosetting (epoxy resins) and thermoplastic (PA-12) polymer matrices with fulleroid and carbon modifiers are synthesized through in situ polymerization, and the mechanical properties are investigated. The introduction of fulleroid modifiers has almost no effect on the mechanical properties of thermosetting formulations; however, in the case of thermoplastic formulations, Young’s modulus and tensile strength increase by 30–40% after introduction of 0.02–0.06 wt % fulleroid modifiers.     

Studies on Poly(Methyl Methacrylate) (PMMA) and Thermoplastic Polyurethane (TPU) Blends

Blends of poly(methyl methacrylate) (PMMA) and thermoplastic polyurethane (TPU) in different compositions viz., 95/5, 90/10, 85/15 and 80/20 (by wt/wt, % of PMMA/TPU) were blended by melt mixing using a twin‐screw extruder. All the PMMA/TPU blends have been characterized for physico‐mechanical properties such as density, melt flow index, tensile behavior and izod impact strength. The impact strength of the PMMA/TPU blends were found to increase significantly with an increase in the percentage of TPU up to 20%, by retaining the tensile strength of PMMA. The effect of chemical aging on the performance of blends has been studied.     

四氢呋喃正离子聚合转为烯类单体负离子嵌段共聚合的研究

本文以癸二酰氯-高氯酸银催化剂在低温引发四氢呋喃正离子聚合,用伯胺终止,制得带有双端仲胺基的聚四氢呋喃遥爪聚合物(PTHF-NHR,R为苄基、正丁基、苯基)。当R为苯基时,PTHF-NHR与萘钠的金属化反应接近完全。以PTHF-NHR的胺钠盐引发烯类单体(甲基丙烯酸甲酯、苯乙烯、丙烯腈)负离子嵌段共聚合。当R为苯基、单体为甲基丙烯酸甲酯时,室温反应可得到转化率为100％的ABA型嵌段共聚物,为热塑性弹性体,其抗张强度为157kg/cm~2,扯断伸长率为700％。     

无水AlCl_3催化PVC/PS反应性增容的研究

以无水AlCl3为催化剂,通过聚氯乙烯(PVC)与聚苯乙烯(PS)之间Friedel-Crafts反应,实现了PVC/PS共混体系的反应性增容,使PVC与PS熔融共混温度由160℃降为140℃;通过预碾磨和加入苯乙烯(St)的方法,提高材料韧性,制备了综合力学性能良好的PVC/PS合金材料.应用FTIR、DSC、SEM和力学性能测试等手段表征了合金材料的结构与性能.结果表明,FTIR出现了1943和838 cm-12个苯环对位被取代的特征吸收峰;DSC在89℃出现了玻璃化转变;SEM证明PVC/PS两相界面粘接性随AlCl3、St的加入越来越好.在PS、AlCl3和St的质量分数分别为6%,0.6%和9%时,实现了对PVC的增强增韧.合金拉伸强度达到60.54MPa,比PVC的49.35 MPa提高了22.7%;缺口冲击强度达到5.3 kJ/m2,比PVC的3.9 kJ/m2提高了35.9%.     

Preparation of Polystyrene/Triphenyl Phosphate Composites by Suspension Polymerization and Melt Extrusion Method——A Comparative Study

Polystyrene (PS)/triphenyl phosphate (TPP) composites were prepared by both suspension polymerization and melt extrusion, and a comparative study of the flame retardance and mechanical properties was carried out. The results showed that suspension polymerization was a better technique than melt extrusion for obtaining good dispersity of the PS/TPP composite. The TPP nanoparticles, which were approximately 50 nm in size, were homogenously and uniformly dispersed in the PS matrix by suspension polymerization in one-step. However, the PS/TPP composite was partially agglomerated, exhibiting irregularly shaped micron-scale particles as a result of melt extrusion. In contrast to the melt extrusion, the limited oxygen index (LOI) of the PS/TPP nanocomposite by suspension polymerization increased to 22.6% from 21.8%, and time to ignition (TTI) increased by 12.3%, the peak heat release rate (PHRR) decreased by 8.5%, and the total heat release (THR) decreased by 11.0%. The mechanical properties of the PS/TPP nanocomposite by suspension polymerization also increased. The tensile strength, elongation at break, and flexural strength increased by 36.4%, 8.5%, and 108%, respectively.