原子转移自由基聚合法接枝改性纳米纤维素及其功能化应用

纳米纤维素不仅具有天然纤维素的基本结构和特性,还具有纳米粒子的独特性能,使其成为众多领域的研究热点。然而,由于纳米纤维素表面存在丰富的羟基,导致表面化学性质单一,需要对其进行化学改性拓宽应用领域。原子转移自由基聚合法(ATRP)能够对纳米纤维素表面进行接枝改性,从而赋予纳米纤维素多样化的功能特性,是纳米纤维素高值化应用的重要方法。本文首先总结了传统ATRP法以及四种新型ATRP法在纳米纤维素表面接枝改性中的应用进展;随后介绍了ATRP法在纳米纤维素端基接枝改性中的应用进展;然后分别介绍了ATRP改性的纳米纤维素接枝共聚物在纳米复合增强、智能响应、环保和生物医疗等领域的应用研究;最后总结了ATRP法改性纳米纤维素存在的难点,并展望了未来ATRP法在纳米纤维素接枝改性领域的发展趋势。     

纳米无机氧化物粒子表面接枝改性

本文对纳米无机氧化物粒子表面的接枝改性作了论述,重点介绍了纳米粒子表面官能团引发的接枝聚合(自由基聚合、阴离子集合、阳离子聚合),并对各种接枝方法以及其发展情况进行了评价。同时对树状接枝进行了简要的介绍。     

表面紫外光接枝聚丙烯酸的聚电解质刷型纳米纤维素晶须

为了研究快速地制备改性纳米纤维素的方法,将低相对分子质量(简称分子量,下同)聚丙烯酸(PAA)以紫外光引发聚合的方法接枝到纳米纤维素晶须上,制备出聚电解质刷型纳米纤维素晶须。采用红外光谱、固体核磁、透射电镜、X射线衍射、热重分析等对刷型纳米纤维素晶须进行了表征测试。考察了单体浓度、光引发剂用量、紫外光照射时间等对接枝聚合反应的影响。结果表明,PAA与纳米纤维素晶须的质量比大于1∶1,光引发剂用量为纳米纤维素晶须质量的0.8%~1.0%,反应时间为90 s时,所得接枝产物中羧基含量最高,达到0.012 75 mol/g。紫外光接枝减少了制备改性纳米纤维素的步骤和时间,将扩展纳米纤维素的表面改性方法和用途。     

两亲嵌段共聚物的合成及其自组装研究进展

作者介绍了两亲嵌段共聚物的活性阴离子聚合、基团转移聚合、开环歧化聚合、活性阳离子聚合、活性／可控自由基聚合、缩聚法、嵌段共聚物化学改性法等合成方法,并对其自组装形成聚合物纳米胶束的制备方法、形成机理以及在药物控制释放领域的应用进行了综述,并对其未来发展趋势进行了展望。     

可控/活性聚合在无机粒子表面接枝研究进展

介绍了一些主要的可控／活性自由基聚合法,包括氮氧调解自由基聚合法（NMRP）、原子转移自由基聚合法（ATRP）、可逆加成断裂链转移聚合法（RAFT）在粒子表面接枝聚合形成无机纳米粒子／聚合物的壳核结构,达到了对粒子改性的目的。并提出了一些目前研究中存在的问题,对可控／活性聚合应用的发展进行了展望。     

通过ATRP法接枝改性无机纳米粒子研究进展

原子转移自由基聚合方法 (ATRP)被广泛的应用在接枝改性无机纳米粒子上等领域。本文介绍了在纳米二氧化钛、二氧化硅等无机纳米粒子上原子转移自由基聚合方法主要的应用,主要可以提高无机纳米粒子的相容性和抗老化性能等特性。但是,最重要的应用是通过原子转移自由基聚合方可以控制接枝物的链的长度及分子量大小,当接枝产物与材料共混时可以更好的改善材料的力学等性能,从而控制并扩大材料的应用范围,同时也使无机纳米的应用领域得到更广泛的应用。本文主要综述了几种原子转移聚合方法对无机粒子的改性应用研究现状。     

原子转移自由基聚合(ATRP)的研究进展

介绍了可以实现活性聚合的ATRP、RATRP、AGET ATRP和ARGET ATRP 4种原子转移自由基聚合的机理,综述了原子转移自由基聚合技术在合成两亲性嵌段共聚物、接枝聚合物和星型共聚物等中的研究进展。     

原子转移自由基聚合在聚合物分子设计中的应用

原子转移自由基聚合反应 ( ATRP)是一种新的活性自由基聚合方法 ,自 1995年提出后 ,引起高分子合成化学及工业界的关注。本文详细介绍了 ATRP在端功能基聚合物、大分子单体、嵌段共聚物、接枝共聚物、星形聚合物、梯度共聚物、超支化聚合物等聚合物分子设计中的应用     

炭黑表面聚合物接枝改性的研究进展

介绍了各种单体通过自由基聚合、阴离子聚合、阳离子聚合等机理在炭黑表面的接技改性及活性聚合物在炭黑表面的接枝反应的研究进展,归纳了改性炭黑的性能及其表征方法。     

聚丙烯酸甲酯接枝改性纳米纤维素

利用羰基二咪唑(CDI)的高活性活化纳米纤维素(NCC),使NCC表面带有高反应活性的碳碳双键。再以2-溴异丁酸乙酯为引发剂,铜丝为催化剂,制备出低分子量的聚丙烯酸甲酯(PMA)。然后采用活性自由基聚合将PMA接枝到活化的NCC表面,制备出PMA接枝改性的NCC。采用凝胶渗透色谱测定合成的PMA的分子量及分子量分布;通过傅立叶变换红外光谱及X射线衍射分析等测试方法对改性前后的NCC的结构和性能进行了分析。实验结果表明,通过单电子转移活性自由基聚合法合成的PMA分子量为2 000,分子量分布窄(分布指数为1.14),并且其成功接枝到NCC表面。     

离子液体中纤维素-甲基丙烯酸羟乙酯的均相聚合

在离子液体介质中利用原子转移自由基聚合方法合成了纤维素-甲基丙烯酸羟乙酯的接枝共聚物,采用甲基丙烯酸羟乙酯单体合成纤维素聚合物,并对聚合物进行结构测定与性质分析。通过FTIR、1HNMR和GPC对聚合物结构及相对分子质量(简称分子量,下同)进行分析,研究了不同溶剂对聚合条件、接枝效率的影响,以及在不同溶剂中聚合物的结构、分子量分布、热稳定性及形态有何变化。结果表明,在溶剂N,N-二甲基甲酰胺(DMF)中进行的反应聚合速率及终止速率均高于在丁酮中进行的反应。纤维素接枝甲基丙烯酸羟乙酯聚合物分子量分布约为1.81,该聚合物热稳定性较强;在DMF中呈球状颗粒,平均直径50 nm;在选择性溶剂丙酮中颗粒直径100 nm左右。     

离子液体中纤维素-甲基丙烯酸羟乙酯的均相聚合

在离子液体介质中利用原子转移自由基聚合方法合成了纤维素一甲基丙烯酸羟乙酯的接枝共聚物,采用甲基丙烯酸羟乙酯单体合成纤维素聚合物,并对聚合物进行结构测定与性质分析。通过FTIR,1H-NMR和GPC对聚合物结构及分子量进行分析,研究了不同溶剂对聚合条件与接枝效率的影响,以及亲水基团的引入聚合物的结构、分子量分布、热稳定性以及在不同溶剂中的形态有何变化。结果表明:在溶剂DMF中进行的反应聚合速率及终止速率均高于在丁酮中进行的反应。纤维素接枝甲基丙烯酸羟乙酯聚合物分子量分布在1.81左右,该聚合物热稳定性较强; 在DMF中呈球状颗粒, 平均直径50nm,在选择性溶剂丙酮中颗粒直径100nm左右     

丙烯酸单体接枝纳米纤维素晶须的研究

以K2S2O8为引发剂,在纳米纤维素晶须(NCW)上接枝丙烯酸单体(AA),制备出丙烯酸接枝改性的纳米纤维素晶须.通过傅立叶变换红外光谱(FTIR)、透射电镜(TEM)、热重分析(TGA)等测试方法对接枝产物的性能进行了分析,并采用电导滴定的方法计算了接枝率以及表面取代基团含量.研究了反应条件对接枝率和接枝效率的影响.结果表明,在引发剂浓度为4 mmol/L,引发时间为5 min,纳米纤维素晶须与丙烯酸单体摩尔比为1: 1.5,反应时间为6 h的条件下,得到了接枝率为14.09%的丙烯酸接枝纳米纤维素晶须.实验证明,在NCW上可以接枝上丙烯酸,接枝率为14.09%的产物与NCW具有相似的表面形貌和热性能;TEM分析可知,接枝产物的分散性得到了提高;表面取代基团含量测试表明,接枝产物表面上的亲水性分散基团含量比NCW增加了5倍以上.     

Grafting polymers from cellulose nanocrystals via surface-initiated atom transfer radical polymerization

Cellulose nanocrystals (CNC) are rod-like nanoparticles extracted from cellulose. Due to their fascinating properties—renewable, biocompatible, non-toxic, biodegradable, excellent mechanical performances, high specific surface area, water dispersible, can be assemble in chiral nematic phases—CNC have shown promise in various fields, including oil recovery, polymer composites reinforcing, hydrogels, aerogels, supercapacitors, energy saving buildings, cosmetics, papermaking, coatings, liquid crystals, and waste water treatment. However, the hydrophilic surface of CNC hinders their broader applications. In this context, surface modification of CNC via polymer grafting can be used to finely tune their surficial properties and endow CNC with a variety of functionalities, such as conductivity, pH or temperature responsiveness, reactivity…In particular, surface-initiated atom transfer radical polymerization (SI-ATRP) is a powerful tool to graft various polymers with a high grafting density and controlled chain length. In this review, the precise control of grafted polymers from CNC via SI-ATRP is first discussed, including issues related to the polymer grafting density, chain length and possibility to perform an asymmetric grafting. Then, the properties and applications of CNC grafted with a variety of polymers are presented. Finally, some challenges and outlook related to the SI-ATRP method applied to the field of CNC is discussed.     

聚合物表面光接枝改性研究进展

表面光接枝主要是用芳酮引发有机材料产生自由基，从而引发单体聚合产生表面接枝链。表面光接枝应用领域广泛．可用于聚合材料的表面改性以及表面功能化。综述了紫外光引发接枝改性聚合物表面的研究进展，包括光接枝聚合机理、改性方法、影响因素等，并对其应用前景及研究方向进行了介绍。     

Modification of hydrophilic cellulose fibers by monolayer growth of polystyrene chains using ATRP

The chemical modification of biopolymer-based materials by grafting synthetic polymers has received considerable attention in recent years, inasmuch as there are wide varieties of monomers available. Nowadays, the most abundant biomacromolecule, cellulose, has attracted considerable attention due to its biodegradable, biocompatible, and renewable characteristics. In this study, the surface of hydrophilic cellulose microfibers was successfully modified by polymerization of hydrophobic polystyrene using atom transfer radical polymerization (ATRP) technique in dispersion medium. In this medium, only the outer surface of the macroinitiator is available for the polymerization, so the grown polymer chains are formed as monolayer on the surface of the macroinitiator. This type of modification not only increases the mechanical properties of the cellulose backbone, but also turns the hydrophilic characteristics of cellulose into hydrophobic state. For this purpose, in the first part of this research, chloroacetylated cellulose was synthesized as macroinitiator. In the second part, the acyl content of the macroinitiator and the degree of substitution, which show the efficiency of the esterification reaction, have been determined by basic hydrolysis of the macroinitiator with KOH and back-titration of the excess alkali with HCl. Finally, the chloroacetylated cellulose was modified by graft copolymerization of styrene using ATRP method. The polystyrene chain growth is confirmed by the atomic force microscopy images.     

ATRP法接枝卤胺分子制备纤维素共聚物抗菌材料

以氯化1-烯丙基-3-甲基咪唑（[AMIM]Cl）离子液体为溶剂,采用原子转移自由基聚合法（ATRP）在微晶纤维素上接枝功能单体N-羟甲基丙烯酰胺,制备了卤胺化合物中间体,应用卤化法将接枝共聚物中的N-H转化为N-Cl键获得具有抗菌性的共聚物材料,并对其抗菌性能进行研究。通过FT-IR、¹H NMR、SEM以及抗菌测试等分析手段表征分析了聚合物的结构、表面形貌和抗菌性能等。结果表明该工艺合成了纤维素接枝N-羟甲基丙烯酰胺共聚物,接枝后表面明显变得粗糙,有利于材料与细菌的接触进而充分发挥其抗菌性能,制备的材料对金黄色葡萄球菌和大肠杆菌均表现出良好抗菌性能,在抗菌材料领域具有较好的应用前景。     

Surface modification of natural substrates by atom transfer radical polymerization

Surface modification of various solid polysaccharide substrates was conducted by grafting methyl acrylate (MA) and styrene via atom transfer radical polymerization (ATRP) to produce well‐defined polymer grafts. The hydroxyl groups on the surfaces of the substrates were reacted with 2‐bromoisobutyryl bromide followed by graft copolymerization under ATRP conditions. The studied substrates were filter paper, microcrystalline cellulose, Lyocell fibers, dialysis tubing, and chitosan films. The modified substrates were analyzed by FT‐IR, water contact angle measurements, TGA, and SEM. FT‐IR characterization of the grafted substrates showed significant differences between the different substrates in the amount of grafted polymer. Higher amounts of polymer seem to be possible to graft from native cellulose substrates than from regenerated cellulose substrates. To investigate whether the grafted polymers were “living” after a longer time period, a second layer of polystyrene was grafted from a filter paper modified with PMA one year ago. FT‐IR characterization of the filter paper showed a peak corresponding to styrene, indicating that a block copolymer had been formed on the surface. Graft copolymerization can be used to change and tailor the surface properties of the polysaccharide substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4155–4162, 2006     

Comparison study of a chiral stationary phase based on cellulose derivatives prepared by “grafting from” and “grafting to” methods

Chiral stationary phase (CSP) with cellulose derivatives was synthesized using the “grafting from” and “grafting to” methods. The “grafting to” method involves the bonding of a preformed end‐functionalized polymer to reactive surface amine groups on the silica gel. The “grafting from” involves the immobilization of initiator onto the aminated silica gel followed by atom transfer radical polymerization (ATRP) to generate the chiral polymer chains. The successful preparation of the CSP with cellulose derivatives prepared by ATRP was confirmed by FE‐SEM, XPS, EA, and thermal analysis. The chiral resolution of the CSP with cellulose derivatives was evaluated by high‐performance liquid chromatography using 10 racemates with various mobile phases that consisted of hexane/alcohol, hexane/THF, and hexane/chloroform. Furthermore, the CSP with cellulose derivatives prepared by “grafting from” and “grafting to” were compared and discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013