Sringam Jiradet, Kajornprai Todsapol, Trongsatitkul Tatiya, Suppakarn Nitinat
School of Polymer Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
Research Center for Biocomposite Materials for Medical Industry and Agricultural and Food Industry, Nakhon Ratchasima 30000, Thailand.
Polymers (Basel). 2025 Jan 17;17(2):225. doi: 10.3390/polym17020225.
Poly(lactic acid) (PLA) exhibits excellent shape memory properties but suffers from brittleness and a high glass transition temperature (T), limiting its utility in flexible and durable applications. This study explored the modification of PLA properties through the incorporation of poly(ethylene glycol) (PEG), varying in both content (5-20 wt%) and molecular weight (4000-12,000 g/mol), to enhance its suitability for specific applications, such as medical splints. The PLA/PEG blend, containing 15 wt% PEG and with a molecular weight of 12,000 g/mol, exhibited superior shape fixity (99.27%) and recovery (95.77%) in shape memory tests conducted at a programming temperature (T) of 45 °C and a recovery temperature (T) of 60 °C. Differential scanning calorimetry (DSC) analysis provided insights into the thermal mechanisms driving shape memory behavior of the PLA/PEG blend. The addition of PEG to the PLA blend resulted in a reduction in T and an increase in crystallinity, thereby facilitating enhanced chain mobility and structural reorganization. These thermal changes enhanced the shape fixity and recovery of the PLA/PEG blend. Synchrotron wide-angle X-ray scattering (WAXS) was further employed to elucidate the microstructural evolution of PLA/PEG blends during the shape memory process. Upon stretching, the PLA/PEG chains aligned predominantly along the tensile direction, reflecting strain-induced orientation. During recovery, the PLA/PEG chains underwent isotropic relaxation, reorganizing into their original configurations. This structural reorganization highlighted the critical role of chain mobility and alignment in driving the shape memory behavior of PLA/PEG blends, enabling them to effectively return to their initial shape. Mechanical testing confirmed that increasing PEG content and molecular weight enhanced elongation at break and impact strength, balancing flexibility and strength. These findings demonstrated that PLA/PEG blends, especially with 15 wt% PEG at 12,000 g/mol, offer an optimal combination of shape memory performance and mechanical properties, positioning them as promising candidates for customizable and biodegradable medical applications.
聚乳酸（PLA）具有出色的形状记忆性能，但存在脆性和高玻璃化转变温度（T）的问题，这限制了其在柔性和耐用应用中的实用性。本研究通过加入聚乙二醇（PEG）来探索对PLA性能的改性，PEG的含量（5 - 20 wt%）和分子量（4000 - 12,000 g/mol）各不相同，以提高其在特定应用（如医用夹板）中的适用性。含有15 wt% PEG且分子量为12,000 g/mol的PLA/PEG共混物，在45 °C的编程温度（T）和60 °C的回复温度（T）下进行的形状记忆测试中，表现出优异的形状固定率（99.27%）和回复率（95.77%）。差示扫描量热法（DSC）分析深入了解了驱动PLA/PEG共混物形状记忆行为的热机制。向PLA共混物中添加PEG导致T降低和结晶度增加，从而促进了链迁移率和结构重组的增强。这些热变化提高了PLA/PEG共混物的形状固定率和回复率。同步辐射广角X射线散射（WAXS）进一步用于阐明PLA/PEG共混物在形状记忆过程中的微观结构演变。拉伸时，PLA/PEG链主要沿拉伸方向排列，反映出应变诱导取向。回复过程中，PLA/PEG链经历各向同性松弛，重新组织成其原始构型。这种结构重组突出了链迁移率和排列在驱动PLA/PEG共混物形状记忆行为中的关键作用，使其能够有效地恢复到初始形状。力学测试证实，增加PEG含量和分子量可提高断裂伸长率和冲击强度，平衡柔韧性和强度。这些发现表明，PLA/PEG共混物，特别是含有15 wt% 12,000 g/mol PEG的共混物，提供了形状记忆性能和力学性能的最佳组合，使其成为可定制和可生物降解医疗应用的有前途的候选材料。
