Effect of end group polarity upon the lower critical solution temperature of poly(2-isopropyl-2-oxazoline)
Effect of end group polarity upon the lower critical solution temperature of poly(2-isopropyl-2-oxazoline)
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DOI：
10.1007/s00396-008-1942-7
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发表时间：
2008-12-01
影响因子：
2.4
通讯作者：
Jordan, Rainer
中科院分区：
文献类型：
--
作者：
Huber, Stephan;Hutter, Naima;Jordan, Rainer
采用引发和终止法对热敏性聚（2-异丙基-2-恶唑啉）（PiPrOx）进行了活性阳离子开环聚合，并与2-甲基-2-恶唑啉进行了序段共聚。甲基、壬基、哌啶、哌嗪以及低聚乙二醇和低聚二甲基恶唑啉作为端基进行了定量介绍。对水溶液的低临界溶解温度进行了研究。疏水端基的引入降低了LCST，而亲水聚合物端基的引入提高了云点。与聚n -异丙基丙烯酰胺相比，端基极性对LCST调制的影响明显更强。令人惊讶的是，末端的低聚乙二醇单元也降低了PiPrOx的LCST，因此与聚（2-恶唑啉）主链相比，它们具有更高的疏水性。与可能的侧基极性变化一起，这允许聚（2-恶唑啉）s的LCST的广泛调制。
Thermo-sensitive poly(2-isopropyl-2-oxazoline)s (PiPrOx) were functionalized with end groups of different polarity by living cationic ring-opening polymerization using the initiator and/or termination method as well as sequential block copolymerization with 2-methyl-2-oxazoline. As end groups, methyl, n-nonyl, piperidine, piperazine as well as oligo(ethylenglygol) and oligo(2-methyl-2-oxazoline) were introduced quantitatively. The lower critical solution temperature (LCST) of the aqueous solutions was investigated. The introduction of hydrophobic end groups decreases the LCST, while hydrophilic polymer tails raise the cloud point. In comparison to poly(N-isopropyl acrylamide), the impact of the end group polarity upon the modulation of the LCST was found to be significantly stronger. Surprisingly, terminal oligoethylenegycol units also decrease the LCST of PiPrOx, thus acting as moieties of higher hydrophobicity as compared to the poly(2-oxazoline) main chain. Together with the possible variation of the side group polarity, this allows a broad modulation of the LCST of poly(2-oxazoline)s.