Immiscibility-miscibility phase transitions in blends of poly(L-lactide) with poly(methyl methacrylate)
Immiscibility-miscibility phase transitions in blends of poly(L-lactide) with poly(methyl methacrylate)
复制标题
DOI：
10.1002/pi.2469
复制
发表时间：
2008-11
影响因子：
3.2
通讯作者：
Shu-Hsien Li;E. Woo
中科院分区：
文献类型：
--
作者：
Shu-Hsien Li;E. Woo
背景技术：采用差示扫描量热法、偏光显微镜、扫描电镜和核磁共振氢谱等方法研究了可生物降解的聚L-乳酸（PLLA）与聚甲基丙烯酸甲酯（PMMA）共混物在加热过程中的相变和明显不可逆的相均匀化。在这个共混体系中的复杂的相行为是令人困惑的，是一个有争议的问题，本研究试图澄清的相行为的真实性质。研究结果：PMMA/PLLA共混物在环境温度下是不混溶的，但在加热至较高温度时可变得混溶，其中上临界溶解温度（UCST）为230 °C。在从UCST快速淬火时，共混物可以冷冻成准混溶状态。在这种状态下，相互作用强度被确定为χ12 =-0.15至-0.19，表明PLLA酯和PMMA丙烯酸羰基之间的相互作用相对较弱。结论：在热均化的PLLA/PMMA共混物中，不存在高于UCST的化学交换反应和通过溶剂再溶解辅助的回到原始相分离形态的相可逆性。在PMMA/PLLA共混物中验证了UCST行为、相图和溶剂辅助相可逆性。版权所有© 2008化学工业协会
BACKGROUND: The nature of phase transitions and apparently irreversible phase homogenization upon heating in blends of biodegradable poly(L-lactide) (PLLA) with poly(methyl methacrylate) (PMMA) were proven using differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy and 1H NMR spectroscopy. The complex phase behaviour in this blend system is puzzling and is a matter of debate; this study attempts to clarify the true nature of the phase behaviour. RESULTS: A PMMA/PLLA blend is immiscible at ambient temperature but can become miscible upon heating to higher temperatures with an upper critical solution temperature (UCST) at 230 °C. The blends, upon rapid quenching from the UCST, can be frozen into a quasi-miscible state. In this state, the interaction strength was determined to be χ12 = − 0.15 to − 0.19, indicating relatively weak interactions between the PLLA ester and PMMA acrylic carbonyl groups. CONCLUSION: The absence of chemical exchange reactions above the UCST and phase reversibility back to the original phase separation morphology, assisted by solvent re-dissolution, in the heat-homogenized PLLA/PMMA blend was shown. Verification of UCST behaviour, phase diagrams and solvent-assisted phase reversibility were experimentally demonstrated in PMMA/PLLA blends. Copyright © 2008 Society of Chemical Industry