Abstract: Polylactic acid (PLA) is an important biodegradable polyester material with good biocompatibility, low toxicity, and good mechanical properties. Its main raw material is starch fermentation in plants, which is renewable and can be degraded by microorganisms (bacteria, fungi, etc.) in nature. As a raw material for plant photosynthesis, PLA enters the natural cycle. There is great potential for application in fields such as green plastics, tissue scaffolds, and biomedicine. However, PLA has poor hydrophilicity and a long degradation cycle, which limits its application in many aspects. So pure PLA materials can no longer meet the growing demand, and modifying them has become a trend.
The chemical modification of PLA mainly involves copolymerization with biodegradable substances to form linear or star-shaped copolymers. Research has found that compared to linear copolymers, star-shaped copolymers have smaller fluid mechanical volume and lower viscosity, indicating better thermal and degradation performance. In addition, plasticizer modification can be targeted at the performance modification of polymers to expand their application fields. Generally, it will choose to copolymerize with hydrophilic substances, such as the commonly used polyethylene glycol (PEG), which can be dissolved in interstitial fluid in the human body, and PEG with molecular weight below 4000 can be quickly eliminated from the body without any toxic and side effects. The addition of PEG can effectively increase the chain mobility of PLA, improve its ductility and stretchability, and thus broaden the potential application range of PLA.
To study the preparation process and hydrophilicity of star-shaped PLA multi block polymers, pentaerythritol (PET) was used as the initiator and stannous octanoate (Sn (Oct) 2) as the catalyst. Star-shaped hydroxyl terminated poly (L-lactide) (s-PLLA) was prepared through ring opening polymerization (ROP), and condensed with polyethylene glycol (PEG, relative molecular weight is 1000) to obtain four arm star-shaped poly (L-lactide) acid polyethylene glycol copolymers (s-PLLA-PEG). The s-PLLA-PEG fiber membrane was successfully prepared by electrospinning, and its surface morphology and hydrophilicity were tested and analyzed. A series of characterization methods were used to confirm the effective synthesis of polymers such as s-PLLA and s-PLLA-PEG. There are currently few reports on the research of PLA-modified fiber membranes. The results show that the melt temperature and glass transition temperature of s-PLLA-PEG decrease, and the flexibility is improved; the contact angle between s-PLLA fiber membrane and water is 132.10°, while the contact angle between the s-PLLA-PEG fiber membrane and water is 84.10°. Over time, the contact angle gradually decreases, and ultimately water is completely absorbed by the fiber membrane, exhibiting stronger hydrophilicity. Research has shown that when PEG is successfully grafted onto s-PLLA, the hydrophilicity of s-PLLA-PEG fiber membranes is significantly better than that of s-PLLA fiber membranes. This indicates that the presence of PEG can effectively improve the hydrophilicity and hydrophobicity of the surface of the s-PLLA fiber membrane, transforming it from a hydrophobic substance to a hydrophilic substance. Due to the excellent hydrophilicity of the s-PLLA-PEG fiber membrane, it has shown certain application prospects in medical dressings.

Key words: star-shaped, poly (L-lactide)-polyethylene glycol copolymer, electrospinning, hydrophilicity

摘要： 星型结构相比较于线型结构具有更稳定的形态和更优异的力学性能。选用季戊四醇（PET）为引发剂，辛酸亚锡（Sn(Oct)2）为催化剂，通过L-丙交酯（L-LA）的开环聚合（ROP）制备星型端羟基聚（L-丙交酯）（s-PLLA），并与聚乙二醇（PEG，相对分子质量为1000）缩合制备四臂星型聚（L-丙交酯）-聚乙二醇共聚物（s-PLLA-PEG）。采用1H-核磁共振、13C-核磁共振、傅里叶变换红外光谱、超高效聚合物色谱仪对产物进行表征，并用静电纺丝技术制备s-PLLA-PEG纤维膜进行亲水性能测试。结果表明：s-PLLA-PEG共聚物成功合成；相对于s-PLLA，s-PLLA-PEG的熔体温度和玻璃化转变温度降低，柔韧性得到改善，韧性增强；s-PLLA-PEG纤维膜对水的接触角是84.10°，随着时间的推移，接触角逐渐减小，最终水被纤维膜完全吸收，相比较s-PLLA纤维膜具有更强的亲水性。该研究表明，PEG嵌段的引入可以有效改善s-PLLA纤维膜的亲水性，展现出静电纺s-PLLA-PEG纤维膜在医用敷料领域的应用前景。

关键词: 星型, 聚（L-丙交酯）-聚乙二醇共聚物, 静电纺丝, 亲水性