Synthesis of Well-Defined Pyrrolidone-Based Homopolymers and Stimulus-Responsive Diblock Copolymers via RAFT Aqueous Solution Polymerization of 2-(N-Acryloyloxy)ethylpyrrolidone.
Synthesis of Well-Defined Pyrrolidone-Based Homopolymers and Stimulus-Responsive Diblock Copolymers via RAFT Aqueous Solution Polymerization of 2-(N-Acryloyloxy)ethylpyrrolidone.
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DOI：
10.1021/acs.macromol.8b01627
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发表时间：
2018-10-09
期刊：
影响因子：
5.5
通讯作者：
Armes SP
中科院分区：
文献类型：
--
作者：
Deane OJ;Lovett JR;Musa OM;Fernyhough A;Armes SP
聚（n -乙烯基吡罗烷酮）（PNVP）是一种众所周知的高极性非离子水溶性聚合物。然而，当n-乙烯基吡罗烷酮（NVP）与甲基丙烯酸或苯乙烯单体共聚时，通常表现出强烈的非理想行为。此外，在活性自由基聚合条件下，NVP并没有得到很好的控制。基于这些原因，人们研究了吡咯烷酮基的替代单体。例如，最近研究了2-（n -甲基丙烯酰氧基）乙基吡咯烷酮（NMEP）的可逆加成-破碎链转移（RAFT）聚合。然而，PNMEP均聚物的亲水性明显低于PNVP，并且在水溶液中表现出相反的温度溶解度。在本工作中，我们研究了2-（n -丙烯酰氧基）乙基吡啶酮（NAEP）在70°C和30°C低温氧化还原引发剂下的RAFT水溶液聚合。PNAEP均聚物产率高（>99%），控制效果好（Mw/Mn < 1.20），目标聚合度（DP）可达400，聚合速度相对较快。然而，以400以上的DPs为目标，NAEP转化率降低，分子量分布更广。通过RAFT水溶液聚合，采用PNAEPx宏观cta对2-丙烯酸羟乙酯（HEA）和低聚（乙二醇）丙烯酸甲醚（OEGA）进行扩链，得到了高转化率（>99%）和良好控制性（Mw/Mn < 1.31）的双亲水丙烯酸二嵌段共聚物。此外，在22°C下，通过n-异丙基丙烯酰胺（NIPAM）的RAFT水溶液聚合，对PNAEP95宏观cta进行了链扩展。动态光散射（DLS）分析表明，加热超过PNIPAM的较低临界溶解温度，在35°C时导致所谓的“反常胶束”，在40°C时形成近单分散的球形胶束。最后，用n- morpholine功能化的三硫代碳素RAFT链转移剂聚合2-（二乙胺）甲基丙烯酸乙酯（DEA），随后用NAEP进行链延伸，形成一种新型的ph响应型二嵌段共聚物。在PDEA的pKa（~ 7.3）以上，DLS和1H NMR研究表明形成了定义良好的PDEA核心球形胶束。
Poly(N-vinylpyrrolidone) (PNVP) is a well-known, highly polar, nonionic water-soluble polymer. However, N-vinylpyrrolidone (NVP) usually exhibits strongly non-ideal behavior when copolymerized with methacrylic or styrenic monomers. Moreover, NVP is not particularly well-controlled under living radical polymerization conditions. For these reasons, alternative pyrrolidone-based monomers have been investigated. For example, the reversible addition–fragmentation chain transfer (RAFT) polymerization of 2-(N-methacryloyloxy)ethylpyrrolidone (NMEP) has been recently investigated using various polymerization formulations. However, PNMEP homopolymers are significantly less hydrophilic than PNVP and exhibit inverse temperature solubility in aqueous solution. In the present work, we studied the RAFT aqueous solution polymerization of 2-(N-acryloyloxy)ethylpyrrolidone (NAEP) using either AIBN at 70 °C or a low-temperature redox initiator at 30 °C. PNAEP homopolymers are obtained in high yield (>99%) with good control (Mw/Mn < 1.20) for target degrees of polymerization (DP) of up to 400 using the latter initiator, which produced relatively fast rates of polymerization. However, targeting DPs above 400 led to lower NAEP conversions and broader molecular weight distributions. 2-Hydroxyethyl acrylate (HEA) and oligo(ethylene glycol) methyl ether acrylate (OEGA) were chain-extended using a PNAEPx macro-CTA via RAFT aqueous solution polymerization, yielding double-hydrophilic acrylic diblock copolymers with high conversions (>99%) and good control (Mw/Mn < 1.31). In addition, a PNAEP95 macro-CTA was chain-extended via RAFT aqueous solution polymerization of N-isopropylacrylamide (NIPAM) at 22 °C. Dynamic light scattering (DLS) analysis indicated that heating above the lower critical solution temperature of PNIPAM led to so-called “anomalous micellization” at 35 °C and the formation of near-monodisperse spherical micelles at 40 °C. Finally, 2-(diethylamino)ethyl methacrylate (DEA) was polymerized using an N-morpholine-functionalized trithiocarbonate-based RAFT chain transfer agent and subsequently chain-extended using NAEP to form a novel pH-responsive diblock copolymer. Above the pKa of PDEA (∼7.3), DLS and 1H NMR studies indicated the formation of well-defined PDEA-core spherical micelles.
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