Petreska Gordana Siljanovska, Sluijs Christof van, 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). 2020 May 30;12(6):1253. doi: 10.3390/polym12061253.
AB diblock waterborne copolymers made of styrene (St) and 2-ethylhexyl acrylate (2EHA) were synthesized by means of two-step reversible addition fragmentation chain transfer (RAFT) (mini)emulsion polymerization. Monofunctional asymmetric RAFT agent was used to initiate the polymerization. The hard polystyrene "A" block was synthesized via miniemulsion polymerization followed by 2EHA pre-emulsion feeding to form the soft "B" block. Polymerization kinetics and the evolution of the molecular weight distribution were followed during synthesis of both initial and final block copolymers. DSC measurements of the block copolymers revealed the existence of two glass transition temperatures (Tgs) and thus the occurrence of two-phase systems. Microscopic techniques (atomic force microscopy (AFM) and transmission electron microscopy (TEM)) were used to study the phase separation within the particles in the latex form, after film formation at room temperature cast directly from the latex and after different post-treatments well above the Tg of the hard-polystyrene domains, when complete particle coalescence had occurred. The morphological differences observed after different annealing temperatures were correlated with the mechanical properties analyzed by DMTA measurements. Finally, the differences found in the mechanical properties of the block copolymers annealed at different temperatures were correlated to their heat seal application results.
通过两步可逆加成-断裂链转移（RAFT）（微）乳液聚合合成了由苯乙烯（St）和丙烯酸2-乙基己酯（2EHA）制成的AB二嵌段水性共聚物。使用单官能不对称RAFT试剂引发聚合反应。通过微乳液聚合合成硬聚苯乙烯“A”嵌段，然后加入2EHA预乳液以形成软“B”嵌段。在初始和最终嵌段共聚物的合成过程中跟踪聚合动力学和分子量分布的演变。嵌段共聚物的DSC测量揭示了两个玻璃化转变温度（Tg）的存在，因此出现了两相体系。使用微观技术（原子力显微镜（AFM）和透射电子显微镜（TEM））研究了以胶乳形式存在的颗粒内的相分离，以及在室温下直接从胶乳浇铸成膜后以及在远高于硬聚苯乙烯域的Tg的不同后处理后（此时发生了完全的颗粒聚结）的相分离。观察到的不同退火温度后的形态差异与通过动态热机械分析（DMTA）测量分析的机械性能相关。最后，在不同温度下退火的嵌段共聚物的机械性能差异与其热封应用结果相关。
