Siljanovska Petreska Gordana, Arbe Arantxa, Auschra Clemens, Paulis Maria
POLYMAT, University of the Basque Country UPV/EHU, Joxe Mari Korta Center, Avda. Tolosa 72, 20018 Donostia-San Sebastián, Spain.
BASF SE, 67056 Ludwigshafen, Germany.
Polymers (Basel). 2019 Jul 30;11(8):1259. doi: 10.3390/polym11081259.
High molecular weight waterborne ABA block copolymers of styrene (St) and 2-ethylhexyl acrylate (2EHA) containing hard and soft domains were synthesized by means of RAFT (mini)emulsion polymerization using a bifunctional symmetric -dibenzyl trithiocarbonate (DBTTC) RAFT agent. Miniemulsion polymerization was initially used for the synthesis of the A-block, which forms hard domains, followed by 2EHA pre-emulsion feeding to build the B-block soft domains. Polymerization kinetics and the evolution of the Molecular Weight Distribution (MWD) were followed during the synthesis of different ABA block copolymers. The thermal properties of the final symmetric block copolymers were studied on dried films by means of DSC. It was found that the block copolymers have two glass transitions, which indicates the presence of a two-phase system. Phase separation was investigated by means of microscopic techniques (AFM and TEM) and SAXS, both of the particles in the latex form, as well as after film formation at room temperature and after different post-treatments. Films were annealed at temperatures well above the glass transition temperature () of the hard phase to study the bulk morphology of the films after complete particle coalescence. Moreover, for comparison purposes, the films were re-dissolved in THF, and films were again cast directly from the homogeneous THF solutions. As THF is a good solvent for both blocks, such films serve as a reference for the equilibrium morphology. Finally, DMTA studies of the films annealed at different temperatures were performed to correlate the morphology changes with the mechanical properties of the block copolymers.
采用双官能团对称二苄基三硫代碳酸酯（DBTTC）RAFT试剂，通过RAFT（微）乳液聚合合成了含有硬段和软段的苯乙烯（St）与丙烯酸2-乙基己酯（2EHA）的高分子量水性ABA嵌段共聚物。微乳液聚合最初用于合成形成硬段的A嵌段，随后加入2EHA预乳液以构建B嵌段软段。在不同ABA嵌段共聚物的合成过程中跟踪聚合动力学和分子量分布（MWD）的演变。通过DSC对干燥膜上最终的对称嵌段共聚物的热性能进行了研究。发现该嵌段共聚物有两个玻璃化转变温度，这表明存在两相体系。通过显微镜技术（AFM和TEM）以及SAXS对乳胶形式的颗粒以及在室温下成膜后和不同后处理后的相分离进行了研究。将膜在远高于硬相玻璃化转变温度（）的温度下退火，以研究颗粒完全聚结后膜的本体形态。此外，为了进行比较，将膜重新溶解在THF中，并再次直接从均匀的THF溶液中浇铸膜。由于THF对两个嵌段都是良溶剂，这样的膜用作平衡形态的参考。最后，对在不同温度下退火的膜进行了动态热机械分析（DMTA），以将形态变化与嵌段共聚物的机械性能相关联。
