Thermogelation of PEG-Based Macromolecules of Controlled Architecture
Thermogelation of PEG-Based Macromolecules of Controlled Architecture
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DOI：
10.1021/ma8025173
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发表时间：
2009-01-13
期刊：
影响因子：
5.5
通讯作者：
Lutz, Jean-Francois
中科院分区：
文献类型：
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作者：
Fechler, Nina;Badi, Nezha;Lutz, Jean-Francois
含低聚乙二醇侧链的接枝(共)聚合物是近年来出现的一类很有前途的新型温敏性聚合物。事实上，这些大分子在大多数情况下，在水溶液或生理介质中表现出定义的较低的临界溶液温度(LCST)。2-5这种热响应行为被认为与这些聚合物的两亲性有关。事实上，亲水性的低聚(乙二醇)侧链与水形成氢键，而主链通常不那么极性，导致竞争性疏水效应。例如，基于聚乙二醇聚乙烯醚、2聚降冰片烯、7聚酯、8聚苯乙烯、9聚丙烯酸酯、10或聚甲基丙烯酸酯4、11主链的低聚乙二醇接枝聚合物在水中都表现出LC ST。尽管如此，最近几年，对后一种类型的研究越来越多。事实上，大多数低聚(乙二醇甲基醚)甲基丙烯酸酯都可以在商业上获得，而且可以很容易地使用多种聚合技术进行聚合，例如原子转移自由基聚合(ATRP)或可逆加成-裂解转移聚合(RAFT)。12例如，我们最近报道了两种不同链长的低聚(乙二醇甲基丙烯酸酯)，即2-(2-甲氧基乙氧基)甲基丙烯酸乙酯(MEO_2MA)和低聚(乙二醇甲基丙烯酸酯)(OEGMA475，Mn)475gmol~(-1)的原子转移自由基共聚合，导致在水中形成具有精确可调LC_(ST)的热响应共聚物。5共聚物P(MEO_2MA-co-OEGMA)的相变是可逆的，对重要参数如共聚物在水中的浓度、离子强度和链长相对不敏感。因此，这些新型聚合物似乎是构建先进刺激响应性材料的有前途的候选者。例如，最近的几篇报道描述了基于低聚乙二醇基的热响应材料的制备，如树枝状大分子、微凝胶、二氧化硅颗粒、金颗粒、嵌段共聚聚合物聚集体、碳纳米管和平面表面。13在本工作中，我们研究了P(MEO_2MA-co-OEGMA)链段用于制备热可逆凝胶网络。生物相容性支架具有可在室温和生理温度之间切换的特性，是再生医学、细胞工程、透皮贴片和植入物等生物技术应用的重要材料。一些合成和生物聚合物已经被证明在水介质中表现出热凝胶行为。特别是含有热响应性聚(N-异丙基丙烯酰胺)(PNIPAM)链段的亲水共聚物(即无规共聚物、嵌段共聚物、接枝共聚物或星形共聚物)在水中通常表现为溶胶-凝胶转变。16、17在这种情况下，PNIPAM链在LcST上方的坍塌导致物理交联。本文合成并表征了基于P(MEO_2MA-co-OEGMA)的可比材料。这项交流的目的是证明低聚(乙二醇甲基丙烯酸酯)构成了在接近生理条件下制备具有最佳性能的生物悬浮热凝胶的独特平台。这些可控网络的构建块是在线形或星形的聚乙二醇大分子引发剂(方案1，左)的存在下由MEO2MA和OEGMA475的ATRP合成的。形成的共聚物具有永久亲水性的聚乙二醇内嵌段和热响应性P(MEO_2MA-co-OEGMA)外嵌段。低于…的最低成本
Graft (co) polymers with oligo (ethylene glycol) side chains emerged lately as a promising new class of thermoresponsive polymers. 1 Indeed, these macromolecules exhibit, for the most part, a defined lower critical solution temperature (LCST) in aqueous or physiological medium. 2-5 This thermoresponsive behavior is believed to be related to the amphiphilic character of these polymers. 6 Indeed, the hydrophilic oligo (ethylene glycol) side chains form H-bonds with water, whereas the backbones, which are usually less polar in nature, lead to a competitive hydrophobic effect. For instance, oligo (ethylene glycol)-grafted polymers based on poly (vinyl ether), 2 poly (norbornene), 7 polyester, 8 polystyrene, 9 poly (acrylate), 10 or poly-(methacrylate) 4, 11 backbones were all reported to exhibit a LCST in water. Still, the latter category has been progressively more studied in recent years. Indeed, most of the oligo (ethylene glycol) methyl ether methacrylates are commercially available and moreover can be readily polymerized using versatile polymerization techniques such as atom transfer radical polymerization (ATRP) or reversible addition-fragmentation transfer polymerization (RAFT). 12 For example, we recently reported that the atom transfer radical copolymerization of two oligo-(ethylene glycol) methacrylates of different chain lengths, namely 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo (ethylene glycol) methacrylate (OEGMA475, Mn) 475 g mol-1), leads to the formation of thermoresponsive copolymers with a precisely tunable LCST in water. 5 The phase transitions measured for the copolymers P (MEO2MA-co-OEGMA) were found to be reversible and relatively insensitive to important parameters such as concentration of the copolymer in water, ionic strength and chain length. 4 Hence, these novel polymers appear as promising candidates for building advanced stimuliresponsive materials. For example, several recent reports described the preparation of oligo (ethylene glycol)-based thermoresponsive materials such as dendrimers, microgels, silica particles, gold particles, block copolymer aggregates, carbon nanotubes, and planar surfaces. 13 In the present work, P (MEO2MA-co-OEGMA) segments were studied for preparing thermoreversible hydrogel networks. Biocompatible scaffolds with switchable properties between room temperature and physiological temperature are materials of high interest for biotechnological applications such as regenerative medicine, cell engineering, transdermal patches, and implants. Some synthetic and biological polymers have already been shown to exhibit a thermogelation behavior in aqueous medium. 14, 15 In particular, hydrophilic copolymers (ie, random, block, graft, or star copolymers) containing thermoresponsive poly (N-isopropylacrylamide)(PNIPAM) segments usually display a sol-gel transition in water. 16, 17 In such cases, the physical cross-linking is induced by the collapse of the PNIPAM chains above LCST. Herein, comparable materials based on P (MEO2MA-co-OEGMA) were synthesized and characterized. The goal of this communication is to demonstrate that oligo (ethylene glycol) methacrylates constitute a unique platform for preparing biorelevant thermogels with optimal properties under near physiological conditions. The building blocks of these controllable networks were synthesized by ATRP of MEO2MA and OEGMA475 in the presence of either linear or star-shaped PEG macroinitiators (Scheme 1, left). The formed copolymers possess permanently hydrophilic PEG inner blocks and thermoresponsive P (MEO2MA-co-OEGMA) outer blocks. Below the LCST of the …