不同引发剂引发SBS接枝马来酸酐的机理研究

采用FTIR和1 H NMR研究了引发剂过氧化二苯甲酰 (BPO)和偶氮二异丁腈 (AIBN)对聚苯乙烯 聚丁二烯 聚苯乙烯 (SBS)接枝马来酸酐 (MAH)的影响 ,讨论了相应的接枝机理 ,通过丁二烯 (PB)段碳碳双键(CC)随接枝率变化的规律进一步验证了机理 .结果表明 ,BPO与AIBN引发接枝的机理不同 ,BPO可引发PB的双键和烯丙位碳氢键 ,但引发烯丙位的速率比引发双键大 ;当BPO浓度达到一定量时 ,大量烯丙位的引发保护了碳碳双键 ,随BPO浓度的增大 ,碳碳双键的含量先减少后增加 .AIBN不能引发PB段烯丙位的碳氢键 ,只能引发双键接枝     

无规聚丙烯接枝甲基丙烯酸的合成

采用溶液聚合的方法将无规聚丙烯 (APP)与甲基丙烯酸 (MAA)接枝共聚制得接枝共聚物APP -g -MAA。讨论了反应温度、反应时间、引发剂BPO浓度、单体MAA浓度对接枝率的影响。结果表明 :当聚合反应温度低于是 12 0℃时 ,接枝率随温度升高而降低。延长反应时间有利于提高接枝率。最适宜的引发剂浓度为 1% ,MAA/APP配比为 0 .2 5/1。利用红外光谱证实了接枝物APP-g -MAA的存在。     

基于正离子聚合方法设计合成接枝共聚物的研究进展

综述了基于可控/活性正离子聚合方法及通过接出接枝(grafting from)、接出接枝(grafting onto)和大分子单体(macromonomer)三种合成策略来设计制备接枝共聚物的研究进展,详细概括了大分子引发剂结构、支链结构、大分子单体结构、大分子链上引发活性点以及官能基团的分布、支链长度及路易斯酸性质等因素对接枝共聚反应的影响规律和不同接枝共聚物的设计合成,总结了上述三种不同合成路径的各自特点,进一步阐述所制备的接枝共聚物在特定环境中的微观结构、形态与外界条件响应性,探讨接枝共聚物的潜在应用领域。     

亲疏水性可控纤维素基相变纤维的制备与性能研究

以棉花为支撑材料,丙烯酰氯(AC)作为中间体,在异相条件下制备纤维素基丙烯酸酯(CA);后利用过氧化苯甲酰(BPO)作为引发剂,通过自由基聚合法接枝疏水性丙烯酸十八酯(A18)、亲水性聚乙二醇单甲醚甲基丙烯酸酯(OEGMA)及其共聚物,制备具有亲疏水性可控的纤维素基固-固相变纤维(solid-solid phase change fibers, SSPCFs)。利用傅里叶变换红外光谱(FTIR)、差示扫描量热仪(DSC)、热重分析(TG)和X射线衍射(XRD)对SSPCFs的结构和热性能进行了表征;通过形态稳定性测试研究接枝共聚物在不同温度下的形态;最后对相变纤维进行水接触角测试研究其亲疏水可控性。结果表明：成功将A18和OEGMA接枝到纤维素表面,制备出具有一定储能特性的固-固相变材料;五种CA-g-P(A18-co-OEGMA)共聚物的耐热温度初始分解温度最低为348℃,最高为368℃,均比CA的初始分解温度高,增加了纤维素基产物的热稳定性;通过水接触角测试表面,随着OEGMA含量的增加,接枝共聚物的水接触角逐渐减小,呈现出逐渐亲水的状态。以上结果说明CA-g-P(A18-co-O...     

β-环糊精/聚(DL-丙交酯)接枝共聚物的合成与表征

以β-环糊精(β-CD)为接枝骨架、DL-丙交酯(DLLA)为接枝单体,三乙胺为催化剂,合成了β-环糊精/聚(DL-丙交酯)接枝共聚物(PCDLA).利用IR、1H-NMR、DSC、WXRD和GPC等方法对接枝共聚物的结构进行了表征,测定了共聚物的分子量,并研究了反应投料比对单体转化率(C%)、接枝率(G%)和接枝效率(GE%)的影响.结果表明,在三乙胺催化下,DL-丙交酯与β-环糊精能够发生聚合反应得到接枝共聚物,当DL-丙交酯与β-环糊精结构单元的摩尔比为30∶1,反应时间为10h时,接枝反应的接枝率(G%)和接枝效率(GE%)可分别达到182·9%和21·4%.随着接枝共聚物中β-环糊精含量的增加,共聚物的亲水性得到了改善.     

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。     

SBS改性沥青机理研究进展

介绍了沥青的特性、苯乙烯-丁二烯-苯乙烯三嵌段共聚物(SBS)的性能,分析了SBS与基质沥青之间的溶胀性和相容性问题,着重论述了SBS改性沥青机理的研究进展,指出机理主要分为物理共混和化学改性两类:物理共混——SBS微粒受到沥青组分中油分的作用发生溶胀而均匀分散在沥青中,SBS与沥青之间没有发生化学作用,只是一种分子间作用力;化学改性——加入添加剂使沥青和SBS之间发生加成、交联或接枝等化学反应,形成较强的共价键或离子键,改善沥青的化学性质。提出化学改性是提高SBS改性沥青路用性能的重要手段。     

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.     

PEB/MMA-AN悬浮接枝共聚反应机理

研究了乙烯-1-丁烯共聚物(PEB)弹性体与甲基丙烯酸甲酯(MMA)-丙烯腈(AN)悬浮接枝共聚反应行为及接枝共聚产物对SAN树脂增韧作用随反应时间的变化规律, 用凝胶渗透色谱法和傅里叶变换红外光谱法对接枝共聚产物进行了表征, 分析了接枝共聚反应机理, 推算了接枝链分子量. 结果表明, 体系首先发生链增长自由基向PEB转移终止形成非接枝共聚物(MAN_L)和PEB大分子自由基引发单体共聚形成接枝链(g-MAN)的反应, 接枝反应结束后体系发生明显的非接枝共聚形成非接枝共聚物(MAN_H)的反应; MAN_L的分子量低于g-MAN的分子量, 而g-MAN的分子量明显低于MAN_H的分子量; 在接枝共聚过程中发生已接枝和未接枝PEB断链并随机再接生成多嵌段共聚物的副反应; 在反应初期, 接枝链的AN单元含量接近于非接枝共聚物的AN单元含量, 在反应中后期前者远低于后者.     

氯化原位接枝反应制备羟基官能化CPE——结构表征

以高密度聚乙烯(HDPE)为基体,采用气-固氯化原位接枝反应合成了以氯化聚乙烯(CPE)为骨架聚合物、丙烯酸-2羟基乙酯(HEA)为支链的接枝共聚物.反应中不需要加入任何引发剂,以氯自由基引发接枝及氯代反应,得到羟基官能化CPE接枝聚合物.并用1H-NMR,FT-IR,GPC及X-射线衍射等对接枝共聚物的结构进行了表征.     

Chemical initiation of graft copolymerization of methyl methacrylate onto styrene–butadiene block copolymer

When a solution containing both styrene–butadiene block copolymer (SBS) and methyl methacrylate is treated with an initiator both homopolymerization of the methyl methacrylate and graft copolymerization of the methyl methacrylate onto the SBS occur. The amount of graft copolymerization depends upon the time and temperature of the reaction, the concentrations of all species, and the identity of the solvent and initiator. The combination of benzoyl peroxide in chloroform gives the highest graft yield and the reaction occurs by removal of an allylic hydrogen from the SBS by the initiator radical and subsequent addition of monomer units to that site; there is a significant solvent effect. Both AIBN and BPO function by the removal of an allylic hydrogen atom from SBS; BPO is able to effect this reaction relatively easily while AIBN can remove the hydrogen atom only with great difficulty and to a limited extent. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 965–974, 1997     

一种双锂引发剂及一步法合成SBS

<正> 目前合成SBS的一般方法是以单锂烷基化合物,按二步法、三步法或偶合法进行,更简便的方法是用双锂引发剂一步法合成SBS。该方法基于苯乙烯、丁二烯彼此间竞聚率差别很大,将两种单体混在一起亦可进行嵌段共聚,与三步法或偶合法的差异是:在聚丁二烯嵌段两端存在着丁苯无规成份,文献称之为“tapered”SBS共聚物。     

两步合成法对SBS结构与性能的研究

<正> 以单官能团烷基锂为引发剂,用两步法合成苯乙烯-丁二烯-苯乙烯(SBS)嵌段共聚物文献中仅见一般性介绍,较为详细的只有Cunningham的研究报告,据认为用n-BuL(正丁基锂)为引发剂时共聚物的物性不佳。我们以环己烷为溶剂,n-BuLi为引发剂,对两步法合成SBS进行了研究。由于在系统中引入了少量THF(四氢呋喃),并找到了消除体系中微量杂质的有效方法,因而试验重复性好,产品物性优良,超过文献值而与Shell公司偶联法工业化产品相近。     

微波辐照下HPMC-g-PMMA的合成及表征

使用微波辐照,在水溶液中以K2S2O8／NaHSO3氧化还原引发体系引发甲基丙烯酸甲酯在羟丙基甲基纤维素上的乳液接枝聚合。讨论了微波辐照下反应时间、单体用量、引发剂浓度、pH值对接枝率的影响,并与水浴条件下的接枝共聚进行了比较。用红外光谱、热重分析、X射线衍射对接枝共聚物进行了表征。测试了其溶解性,结果表明接枝物具有良好的抗有机溶剂以及强酸、强碱的性能。     

Effect of grafted methyl methacrylate on the catalytic hydrogenation of natural rubber

The graft copolymerization of methyl methacrylate onto natural rubber was carried out by using a cumene hydroperoxide redox initiator. The graft copolymer was purified by extraction and then hydrogenated in the presence of OsHCl(CO)(O₂)(PCy₃)₂. The graft copolymer and hydrogenated product were characterized by proton nuclear magnetic resonance (¹H NMR). The rate of hydrogenation was investigated using a gas-uptake apparatus. The hydrogenation was observed to be inverse first-order with respect to rubber concentration. The addition of a small amount of poly(methyl methacrylate) demonstrated a beneficial effect on the hydrogenation of the grafted copolymer.     

Process parameters and their effect on grafting reactions in core/shell latexes

The grafting of methyl methacrylate (MMA) onto polybutadiene (PB) latexes prepared by seeded emulsion polymerization at 50°C was investigated as a function of: (a) initiator concentration used in the secondary polymerization, (b) monomer-to-polymer ratio, (c) the specific surface area of the seed latex, and (d) the degree of conversion. The thin layer chromatography/flame ionization detection (TLC/FID) technique was used to determine the proportion of graft copolymer in the core/shell latex, It was found that grafting PMMA onto PB depended upon the concentration of initiator, decreasing as the concentration was increased. The amount of grafting increased with increasing specific surface area of the seed latex, while the molecular weight of the acetone-soluble graft copolymer decreased. The amount of graft copolymer was found to decrease concurrently with increasing monomer-to-polymer ratio and degree of conversion. These results suggest a hydrogen abstraction mechanism in the formation of graft PB–PMMA through a chain transfer process.     

两性纤维素接枝共聚物的研究Ⅰ. 两性共聚物的合成

用过硫酸铵和四甲基乙二胺氧化还原引发体系合成了羧甲基纤维素接枝甲基丙烯酸二甲胺基乙酯两性共聚物（ＣＧＤ）,研究了反应温度、ｐＨ、原料羧甲基取代度、引发剂用量、反应物料配比和外加盐对接枝共聚的影响,并用红外光谱对接枝共聚物结构进行了鉴定     

Grafting onto Starch. IV. Graft Copolymerization of Methyl Methacrylate by Use of AIBN as Radical Initiator

Grafting of poly(methyl methacrylate) onto starch has been investigated in aqueous medium by using AIBN as radical initiator. Starch-g-PMMA has been characterized by determination of starch in the graft copolymer. Percentage of grafting has been determined as functions of concentration of monomer, concentration of initiator, reaction time, and temperature. From scanning electron microscopic studies, evidence for grafting of PMMA onto starch has been presented.     

Preparation of a copolymer of methyl methacrylate with a new monomer, 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate,and its initiation of the graft copolymerization of styrene with a controlled radical mechanism

A copolymer [P(MMA‐co‐TBPM)] was prepared by the radical polymerization of methyl methacrylate (MMA) and 2,2,6,6‐tetramethyl‐4‐benzyloxyl‐piperidinyl methacrylate (TBPM) with azobisisobutyronitrile as an initiator. TBPM was a new monomer containing an activated ester. Both the copolymer and TBPM were characterized with NMR, IR, and gel permeation chromatography in detail. It was confirmed that P(MMA‐co‐TBPM) could initiate the graft polymerization of styrene by the cleavage of the activated ester of the TBPM segment. This process was controllable, and the molecular weight of the graft chain of polystyrene increased with the increment of conversion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4398–4403, 2002     

Synthesis and Characterization of CPE-g-GMA Graft Copolymers Obtained by Suspension Copolymerization

Graft of glycidyl methacrylate (GMA) onto solid-state chlorinated polyethylene (CPE) has been performed by suspension copolymerization in a complex dispersion medium which was a compound with H₂O, ethyl acetate (EA) and tert-butyl alcohol (TBA). Benzoyl peroxide (BPO) was used as the free radical initiator. The graft level (graft degree and graft efficiency) was calculated gravimetrically, and the graft copolymer was characterized by infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and contact angle study. The effects of reaction conditions on graft level, including chemical parameters (the concentration of monomer, initiator, and interfacial agent) and processing parameters (reaction time and temperature), have been investigated in detail. The experimental results showed that GMA could be grafted onto the chain of CPE with comparative higher graft degree, which could reach 37% with graft efficiency above 80%.