聚(苯乙烯-马来酸酐)/Fe3O4纳米杂化材料的制备与表征

采用2,2,6,6-四甲基-1-哌啶氧化物(TEMPO)的溴盐对化学共沉淀法制备的Fe3O4纳米粒子进行表面修饰,以该粒子为过氧引发剂,苯乙烯(St)、马来酸酐(MA)为单体,采用"活性"/可控自由基聚合技术在粒子表面原位引发聚合,制备了聚(苯乙烯-马来酸酐)/Fe3O4纳米杂化材料,并对纳米Fe3O4及杂化材料进行了FT-IR、XRD、TGA、TEM和GPC表征。结果表明,所制备的纳米杂化材料的平均粒径约为70 nm,磁性粒子表面的聚合物分子链随着聚合时间的增长而增长。振动样品磁强计测试结果显示,在室温、外加磁场下,该纳米杂化材料呈现超顺磁性,饱和磁化强度随着包覆聚合物量的增加而降低。     

RAFT聚合制备PBMA/AA-SiO2杂化纳米材料

以三硫代二[4-(甲氧羰基)苄基]碳酸酯为链转移剂(CTA),甲基丙烯酸丁酯(BMA)为单体,通过可逆加成-断裂链转移自由基聚合(RAFT)法修饰丙烯酸(AA)功能化的纳米二氧化硅(SiO2),制备了PBMA/AA-SiO2有机/无机杂化纳米材料。并通过FT-IR、GPC、TGA、TEM表征和分析了杂化材料的结构、分子量、SiO2纳米粒子在基体中的分散性以及杂化材料的热稳定性。结果表明,PBMA/AA-SiO2杂化微球粒径约为22 nm,分布均匀;TGA分析表明此杂化材料的热稳定性良好,PBMA接枝率为19%。     

无机纳米材料表面引发自由基可控聚合反应

无机纳米-高分子杂化材料具有优异的性能及广阔的应用前景,引起人们的广泛关注.本文综述了无机纳米材料表面引发自由基可控聚合反应在合成无机-高分子纳米杂化材料方面的广泛应用,包括表面引发原子转移自由基聚合(ATRP)、表面引发可逆加成-断裂链转移自由基聚合(RAFT)、表面引发稳定氮氧自由基聚合(NMP). 着重总结了近几年来这类杂化材料在功能性研究上新的进展,并对今后研究的发展趋势进行了展望.     

SiO2表面RAFT接枝聚合苯乙烯

基于纳米SiO2表面羟基与7-甲基丙烯酰氧基丙基三甲氧基硅烷间的偶联反应,在纳米SiO2表面引入可聚合双键。采用可逆加成断裂链转移（RAFT）聚合技术,以偶氮二异丁腈为引发剂,使SiO2表面接枝聚合苯乙烯。考察了二硫代苯甲酸异丁腈酯、二硫代苯甲酸苄酯、（1,2,4-三氮唑）基二硫代甲酸苄酯和二硫代新戊酸苄酯等对SiO2表面接枝聚合苯乙烯速率的影响。结果表明,SiO2表面接枝聚合苯乙烯的速率决定于RAFT试剂的Z基团结构。二硫代新戊酸苄酯调控的SiO2表面接枝聚合苯乙烯的速率最高。     

超支化聚乙烯亚胺接枝二氧化硅的制备及在聚丙烯改性中的应用

首先利用3-缩水甘油氧基丙基三甲氧基硅烷(简称GPS)作为偶联剂,对纳米SiO2进行表面改性,获得表面含有环氧基的SiO2纳米粒子(SiO2-GPS).利用这些环氧基与超支化聚乙烯亚胺(HPEI)分子中的氨基进行反应,得到SiO2接枝超支化聚乙烯亚胺的纳米粒子(SiO2-GPS-g-HPEI).然后利用SiO2-GPS-g-HPEI与聚丙烯(PP)和PP接枝的马来酸酐(PP-g-MAH)共混、模压,制备PP/SiO2-GPS-g-HPEI/PP-g-MAH复合材料.红外光谱测试和热失重分析(TGA)测试结果表明,SiO2纳米粒子表面依次接枝了GPS和HPEI;扫描电子显微镜(SEM)的测试结果显示,SiO2-GPS-g-HPEI在聚丙烯基体中分散良好,其材料的冲击断裂为韧性断裂;复合材料共混时,扭矩的增加证明了共混物中分散相(SiO2-GPS-g-HPEI)与基体(PP/PP-g-MAH)界面之间存在一定的相互作用.少量SiO2-GPS-g-HPEI加入PP/PP-g-MAH中,冲击强度可增加96.3%,拉伸强度也有较大的提高.     

聚(苯乙烯-alt-马来酸酐)-b-聚苯乙烯亲水/亲油嵌段共聚物在溶液中的聚集行为研究

采用RAFT方法合成了由马来酸酐／苯乙烯和苯乙烯组成的交替序列两嵌段共聚物P(MAn-alt-St)-b-PSt。将其中的马来酸酐用PEO进行水解,得到了支化的亲水亲油两嵌段共聚物。通过H—NMR和IR对共聚物的结构组成进行表征。以二甲基氨基黄酮化舍物为荧光探针,测定了形成共聚物胶束的临界浓度(CMC)。用TEM和SEM现察不同酸碱条件下所得纳米材料形貌,并对其形成机制进行了讨论。     

通过RAFT法制备聚合物/膨润土杂化材料

通过可逆加成-断裂链转移(RAFT)自由基聚合方法合成了聚合物/膨润土(蒙脱石)杂化材料. 以乙基黄原酸基膨润土为链转移剂, AIBN为引发剂, 在环己酮溶液中, 通过甲基丙烯酸甲酯的RAFT自由基聚合, 得到了一系列的聚合物/膨润土杂化材料. 并用FT-IR, NMR, SPM, TG, GPC等分别对产物的微观结构、热性能、有机物含量以及分子量和分子量分布进行了表征和测试.     

Fe3O4/C磁性多孔碳材料的制备及其对品红的吸附

采用可逆加成—断裂链转移法(RAFT)合成了嵌段共聚物聚(苯乙烯-co-马来酸酐)-b-聚乙二醇甲基丙烯酸酯(PSMA-b-PMAPEG),并以该嵌段共聚物为软模版,以盐酸多巴胺(DA)作为碳源,将其包覆在Fe_3O_4纳米颗粒上,再经高温灼烧得到具有多孔结构的Fe_3O_4/C磁性复合微球.通过扫描电镜(SEM)、红外光谱(FT-IR)、X射线粉末衍射(XRD)、振动磁强计(VSM)、N_2吸附/脱附等手段对该多孔材料进行了表征.同时考察了Fe_3O_4/C磁性多孔材料的吸附性能,研究表明该多孔材料对品红表现出了良好的吸附效果.     

可聚合纳米SiO2杂化材料的制备及其性能研究

利用异佛尔酮二异氰酸酯(IPDI)和纳米SiO2表面-OH基团反应的特点,制备了表面含-NCO基团的纳米SiO2,用端羟基聚丙二醇醚(PPG)对其扩链并进一步和丙烯酸羟乙酯(HEA)反应,制备了丙烯酸酯封端、IPDI和PPG连接纳米SiO2粒子的纳米SiO2杂化材料.用红外光谱(FTIR)、热失重(TGA)和扫描电镜(...     

基于点击化学和活性自由基聚合方法制备双重响应金纳米粒子

采用点击化学和可逆加成断裂链转移活性自由基聚合方法制备了温度和pH双重响应的金纳米粒子. 通过红外光谱(FTIR)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)及热重分析(TGA)等方法对双重响应性金纳米粒子进行了表征. 该金纳米杂化粒子具有良好的分散性, 其表面接枝聚合物的密度约为0.6 Chain/nm2. 通过改变温度和pH条件, 考察了金纳米杂化粒子的可逆响应行为. 实验结果表明, 点击化学和可逆加成断裂链转移活性自由基聚合方法实现了金纳米粒子修饰的简单化、可控化以及功能化.     

Block and star block copolymers by mechanism transformation X. Synthesis of poly(ethylene oxide) methyl ether/polystyrene/poly(l-lactide) ABC miktoarm star copolymers by combination of RAFT and ROP

Poly(ethylene oxide) methyl ether/polystyrene/poly(l-lactide) (MPEO/PSt/PLLA) ABC miktoarm star copolymers were synthesized by combination of reversible addition-fragmentation transfer (RAFT) polymerization and ring-opening polymerization (ROP) using bifunctional macro-transfer agent, MPEO with two terminal dithiobenzoate and hydroxyl groups. It was prepared by reaction of MPEO with maleic anhydride (MAh), subsequently reacted with dithiobenzoic acid and ethylene oxide. RAFT polymerization of St at 110 °C yielded block copolymer, MPEO-b-PSt [(MPEO)(PSt)CH₂OH], and then it was used to initiate the polymerization of l-lactide in the presence of Sn(OCt)₂ at 115 °C to produce ABC miktoarm star polymers, s-[(MPEO)(PSt)(PLLA)]. The structures of products obtained at each synthetic step were confirmed by NMR and gel permeation chromatography data.     

次价键力在化学键合法固定辣根过氧化酶过程中的作用机理

将甲基丙烯酸缩水甘油酯(GMA)接枝聚合在微米级硅胶微粒表面,又通过环氧基团的开环反应将乙二胺(EDA)键合在接枝微粒表面,制备了双功能复合载体EDA-PGMA/SiO2,通过共价偶联法实施了辣根过氧化酶(HRP)的固定化.本文重点考察静电相互作用与疏水相互作用两种次价键力在共价键合法固定HRP过程中的作用,探讨作用机理.结果表明,在水介质中,复合载体EDA-PGMA/SiO2表面胺基的质子化作用,使载体微粒的ζ电位在较大的pH范围内保持正值;当介质的pH=8.5,大于HRP的等电点时,酶蛋白与载体之间所产生的强静电相互作用会显著促进HRP的固定化;EDA的键合率在30％附近的载体,静电相互作用对固酶的促进作用最强,固定化酶的偶联率与比活力具有最高值.疏水相互作用对化学法固定辣根过氧化酶也会产生明显的作用,当以接枝微粒PGMA/SiO2为载体时,增大NaCl浓度,可有效促进酶蛋白与载体之间的疏水相互作用,提高固定化酶的偶联率与比活力.     

Grafting from ramie fiber with poly(MMA) or poly(MA) via reversible addition-fragmentation chain transfer polymerization

Reversible addition-fragmentation chain transfer (RAFT) polymerization was utilized to control the grafting of methyl methacrylate (MMA) and methyl acrylate (MA) from natural ramie fibers substrate. The hydroxyl groups of ramie fibers were first converted to 2-dithiobenzoyl isobutyrate as a RAFT chain transfer agent (CTA), which was further grafted with MMA or MA mediated by the RAFT polymerization in a presence of 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate as a free chain transfer agent. Hydrophobic poly(MMA) or poly(MA) modified ramie fibers with contact angles greater than 130° were obtained. The modified ramie fibers were analyzed by gravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetry and contact angle measurements. The results indicate that the polymer chains had indeed been grafted from the surface of the ramie fibers with an average 33% of the hydroxyl groups in the raw ramie fiber substituted by 2-bromoisobutyryl bromide and an average grafting ratio of 25% poly(MMA) or poly(MA) related to ramie fiber. The homopolymers formed in the copolymerization were also analyzed to estimate molecular weights and polydispersity indices of grafting chains from the surface of ramie fibers by size exclusion chromatography, which showed narrow polydispersity with the PDIs to be <1.32. This study provides a novel and feasible approach to the preparation of functional composite materials for utilizing the abundant natural ramie fiber cellulose resource.     

Synthesis and Characterization of Poly(methyl methacrylate)-b-Polystyrene/TiO2 Nanocomposites Via Reversible Addition-Fragmentation Chain Transfer Polymerization

A diblock copolymer, poly(methyl methacrylate)-b-polystyrene (PMMA-b-PS), was grafted onto the surface of nano-titania (nano-TiO₂) successfully via reversible addition-fragmentation chain transfer (RAFT) polymerization. The surface of TiO₂ nanoparticles was modified initially by attaching dithioester groups to the surface using silane coupling agent 3-(chloropropyl)triethoxy silane and sodium ethyl xanthate. The polymerization of methyl methacrylate and styrene were then initiated and propagated on the TiO₂ surface by RAFT polymerization. The resulting composite nanoparticles were characterized by means of XPS, FT-IR, ¹H NMR and TGA. The results confirmed the successful grafting of poly(methyl methacrylate) (PMMA) and diblock copolymer chains onto the surface of TiO₂. The amount of PMMA grafted onto the TiO₂ surface increased with the polymerization time. Moreover, the kinetic studies revealed that the ln([M]₀/[M]), where [M]₀ is the initial and [M] is the time dependent monomer concentrations, increased linearly with the polymerization time, indicating the living characteristics of the RAFT polymerization.     

SiO_2/PVAc无机-有机复合微球的合成及其膜性能研究

以纳米二氧化硅粒子(SiO2)为稳定剂,在少量反应型阴离子乳化剂——烯丙氧基羟丙磺酸钠(HAPS)作助稳定剂的情况下,制备了具有草莓型结构的二氧化硅/聚醋酸乙烯酯(SiO2/PVAc)无机-有机纳米复合微球.研究表明,纳米SiO2与PVAc的氢键作用是形成这种单分散草莓型SiO2/PVAc无机-有机纳米复合微球的关键.透射电镜(TEM)观察显示,纳米SiO2吸附在PVAc表面,形成草莓型结构.讨论了纳米二氧化硅溶胶的种类和用量、乳化剂种类对复合微球形态及其膜性能的影响,并讨论了复合微球的形成机理.     

Surface grafting of polymers onto inorganic ultrafine particles: Reaction of functional polymers with acid anhydride groups introduced onto inorganic ultrafine particles

The surface grafting onto inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by the reaction of acid anhydride groups on the surfaces with functional polymers having hydroxyl and amino groups was examined. The introduction of acid anhydride groups onto inorganic ultrafine particle was achieved by the reaction of hydroxyl groups on these surfaces with 4-trimethoxysilyltetrahydrophthalic anhydride in toluene. The amount of acid anhydride groups introduced onto the surface of ultrafine silica, titanium oxide, and ferrite was determined to be 0.96, 0.47, and 0.31 mmol/g, respectively, by elemental analysis. Functional polymers having terminal hydroxyl or amino groups, such as diol-type poly(propylene glycol) (PPG), and diamine-type polydimethylsiloxane (SDA), reacted with acid anhydride groups on these ultrafine particles to give polymer-grafted ultrafine particles: PPG and SDA were considered to be grafted onto these surfaces with ester and amide bond, respectively. The percentage of grafting increased with increasing acid anhydride group content of the surface: the percentage of grafting of SDA (M_n = 3.9 × 10³) onto silica, titanium oxide, and ferrite reaching 64.7, 33.7, and 24.1%, respectively. These polymer-grafted ultrafine particles gave a stable colloidal dispersion in organic solvents.     

Structure control in PMMA/silica hybrid nanoparticles by surface functionalization

Hydrophilic silica particles need to be hydrophobized to be encapsulated in a polymeric environment, which can be achieved by different methods. We report on the relationship between different hydrophobization techniques of silica and the final structure of poly(methyl methacrylate)/silica hybrid nanoparticles obtained by miniemulsion polymerization. Hydrophobization by cetyltrimethylammonium chloride (CTMA-Cl) uses the ionic interaction between the positively charged ammonium salt and the negatively charged silica surface, as shown by isothermal titration calorimetry. In this case, the interaction between polymer and silica surface needs to be enhanced, so 4-vinylpyridine (4-VP) was used as a co-monomer. Alternatively, the condensation reactions of 3-methacryloxypropyltrimethoxysilane (MPS) and octadecyltrimethoxysilane (ODTMS) were used to provide a covalent bond to the silica surface. The condensation reaction of the trimethoxysilane groups onto the silica surface was proven by Fourier transform infrared spectroscopy and thermogravimetric analysis. Hybrid nanoparticles were successfully formed with silica particles functionalized with the different functionalization agents. However, the structure of the resulting hybrid particles (i.e., the distribution of the silica particles within the polymer matrix) depends on the agent. The MPS-functionalized silica particles copolymerize with poly(methyl methacrylate), leading to a fixation of the silica particles inside the polymer and to a homogeneous distribution. The CTMA-Cl- and ODTMS-functionalized silica particles cannot copolymerize, but aggregate at the interface, leading to a Janus-like structure.     

Synthesis and characterizations of poly(ethylene oxide) methyl ether grafted on the expanded graphite with isocyanate groups

Introducing isocyanate (NCO) groups onto the surface of expanded graphite (EG) was achieved by treatment of the EG with excess toluene-2,4-diisocyanate in dimethyl sulfoxide (DMSO). The reaction of NCO group on the EG with the hydroxyl group in the poly(ethylene oxide) methyl ether (MPEO) to yield MPEO-grafted EG was carried out for modifying the surface properties of graphite. The influence factors, such as reaction time, temperature and the ratio of the reactants, on the grafting reaction and grafting ratio were investigated.     

Synthesis of poly(methyl acrylate) loops grafted onto silica nanoparticles via reversible addition‐fragmentation chain transfer polymerization

Reversible addition‐fragmentation chain transfer (RAFT) polymerization was used to produce poly(methyl acrylate) (pMA) loops grafted onto silica nanoparticles using doubly anchored bifunctional RAFT agents 1,4‐bis(3′‐trimethoxysilylpropyltrithiocarbonylmethyl)benzene (Z‐group approach) and 1,6‐bis(o,p‐2′‐trimethoxysilylethylbenzyltrithiocarbonyl)hexane (R‐group approach) as mediators. In both cases, molecular weights of the resulting surface‐confined polymer loops increased with monomer conversion, whereas the grafting density was significantly higher in the case of the R‐group supported RAFT polymerization due to mechanistic differences of the RAFT process at the surface. This result was evident from thermogravimetric analysis and supported by scanning electron microscopy. Polymer loops with molecular weights up to 53,000 g mol^?1 were accessible with polydispersities of about 2.0 without and 1.5 with the addition of free RAFT agent. UV signals of the detached pMA loops measured via size exclusion chromatography were shifted to higher molecular weights compared with the corresponding RI signals, indicating branching reactions caused by the close proximity of growing radicals and polymer at the surface of the silica nanoparticles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7656–7666, 2008     

硅胶表面铜(Ⅱ)离子印迹聚乙烯亚胺的制备及结合特性研究

通过γ-氯丙基三甲氧基硅烷的媒介,将聚乙烯亚胺(PEI)偶合接枝到硅胶微粒表面,形成了化学键联的复合材料PEI/SiO2;以Cu2+为模板离子,以环氧氯丙烷为交联剂,通过配位键作用,对化学键合在硅胶表面的PEI大分子链进行了离子印迹,制备了复合型Cu2+印迹材料IIP-PEI/SiO2;采用静态与动态两种方法研究了IIP-PEI/SiO2对Cu2+的结合特性,并考察了主要印迹条件Cu2+浓度及环氧氯丙烷用量对印迹材料吸附性能的影响.结果表明,Cu2+印迹材料IIP-PEI/SiO2对Cu2+具有强的记忆识别能力,主要表现在两个方面,(1)对Cu2+的结合量大,IIP-PEI/SiO2对Cu2+的吸附容量比印迹前复合材料PEI/SiO2提高了近2倍;(2)对Cu2+的选择性高,相对于Cd2+,IIP-PEI/SiO2对Cu2+的选择性系数为83.79,相对于Zn2+,IIP-PEI/SiO2对Cu2+的选择性系数为80.21.另外印迹材料IIP-PEI/SiO2具有优良的洗脱与再生性能.