【作者】 郭涛；

【导师】 张风华；

【作者基本信息】 哈尔滨工业大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 形状记忆聚合物虽然已经广泛应用于航空航天、生物医疗等领域,但在精密制造和小尺寸器件的领域中应用较少;因此,学者们开展了形状记忆聚合物微纳米尺寸领域的研究。聚合物微球因其具备可控、可负载药物等优点,被广泛应用于生物医学领域。本论文设计并制备了适用于人体口腔温度区间的形状记忆聚合物复合材料,即采用O/W乳化溶剂挥发法制备了形状记忆微球,研究了制备参数对微球粒径及形貌的影响,并在微球中引入磁性颗粒赋予其磁定向运动的功能性。通过扫描电子显微镜、倒置光学显微镜验证了形状记忆聚合物微球的磁定向运动、形状记忆的功能,实现了形状记忆微球封闭牙本质小管的功能验证。针对聚乳酸（PLA）的变形温度远高于人体口腔耐受温度的问题,通过物理共混的方法将不同比例的柠檬酸三丁酯（TBC）与PLA混合,制备出一系列低玻璃化转变温度（T_g）的PLA/TBC材料,并对其热学、形状记忆性能进行调控。当材料中PLA/TBC的质量比为85/15时,材料的形状记忆温度降至40℃,材料可在21 s回复至初始形状的99%以上。通过在该材料体系中引入油酸改性的纳米Fe₃O₄颗粒以赋予材料磁定向运动等功能性;当Fe₃O₄颗粒含量为15wt.%时,PLA/TBC/Fe₃O₄复合材料可分别在40℃的热源、808 nm近红外光源、30 k Hz交变磁场的作用下实现形状记忆功能。通过O/W乳化溶剂挥发法将上述PLA85/TBC15材料制备成微球,研究不同制备参数对微球粒径及形貌的影响,例如油相聚合物的浓度、水相乳化剂的浓度和分散机的搅拌速度。聚合物浓度为10 mg/m L、乳化剂浓度为1wt.%、搅拌速度为7000 rpm时,微球具有最佳形貌,与牙本质小管的直径相似。随后,在微球中引入不同类型的纳米Fe₃O₄颗粒,探究了不同类型的磁性颗粒在微球中的分布情况。扫描电子显微镜及透射电子显微镜的观察结果表明,与普通的Fe₃O₄颗粒相比油酸改性的Fe₃O₄颗粒更易被PLA/TBC微球包覆,且可以均匀的分散在微球的内部,有利于微球在外界磁场的条件下定向运动。通过光学显微镜及扫描电子显微镜验证了PLA/TBC/Fe₃O₄微球的磁定向运动、形状记忆功能,并通过体内/外细胞毒性实验验证了PLA/TBC/Fe₃O₄微球的生物安全性,而后对形状记忆PLA/TBC/Fe₃O₄微球封堵牙本质小管的效果进行了观察与评估。磁性颗粒含量为15wt.%的PLA/TBC/Fe₃O₄微球具备在外加磁场的作用下定向运动以及在40℃热源下形状记忆的能力,此外浓度在500μL/mg范围内的PLA/TBC/Fe₃O₄微球对于细胞的增殖具有一定的促进作用,具备良好的生物安全性。在外加磁场的作用下椭球形的PLA/TBC/Fe₃O₄微球可以深入牙本质小管内部29μm处,并在40℃的热源下回复至球形实现封堵,形状记忆PLA/TBC/Fe₃O₄微球的进入率为85.41±7.11%,封堵率为93.33±2.82%。更多还原

【Abstract】 Although shape memory polymers have been widely used in aerospace and biomedical fields,they are less used in the field of precision manufacturing and small-sized devices;therefore,scholars have carried out research in the field of shape memory polymers micro-and nano-sized.Polymer microspheres are widely used in biomedical fields because of their advantages such as controllable and drug-loadable.In this thesis,shape memory polymer composites suitable for human oral temperature range were designed and prepared,i.e.,shape memory microspheres were prepared by O/W emulsion solvent volatilization method,and the effects of preparation parameters on the particle size and morphology of microspheres were investigated,and magnetic particles were introduced into the microspheres to give them the functionality of magnetic directional motion.The magnetic directional motion and shape memory function of the shape memory polymer microspheres were verified by scanning electron microscopy and inverted optical microscopy,and the functional verification of the shape memory microspheres to seal the dentin tubules was realized.To address the problem that the deformation temperature of poly（lactic acid）（PLA）is much higher than the human oral tolerance temperature,a series of PLA/TBC materials with low glass transition temperature（T_g）were prepared by mixing different ratios of tributyl citrate（TBC）with PLA through a physical blending method,and their thermal and shape memory properties were tuned.When the mass ratio of PLA/TBC in the material was 85/15,the shape memory temperature of the material was reduced to 40°C and the material could return to more than 99%of its initial shape in 21 s.By introducing oleic acid-modified Fe₃O₄ nanoparticles into the material system to impart functionalities such as magnetic directional motion;when the Fe₃O₄ particle content is 15 wt.%,the PLA/TBC/Fe₃O₄ composite can achieve shape memory function under the action of heat source at 40°C,808 nm NIR light source,and 30 k Hz alternating magnetic field,respectively.The above PLA85/TBC15 materials were prepared into microspheres by the O/W emulsification solvent volatilization method,and the effects of different preparation parameters on the particle size and morphology of the microspheres,such as the concentration of the polymer in the oil phase,the concentration of the emulsifier in the aqueous phase,and the stirring speed of the disperser,were investigated.Microspheres with a polymer concentration of 10 mg/m L,an emulsifier concentration of 1 wt.%,and a stirring speed of 7000 rpm had the best morphology,similar to the diameter of dentin tubules.Subsequently,the distribution of different types of magnetic particles in the microspheres was investigated by introducing different types of Fe₃O₄ nanoparticles into the microspheres.The observation results of scanning electron microscopy and transmission electron microscopy showed that the oleic acid-modified Fe₃O₄ particles were more easily encapsulated by PLA/TBC microspheres compared with ordinary Fe₃O₄ particles and could be uniformly dispersed inside the microspheres,which was beneficial to the directional motion of the microspheres under the conditions of external magnetic field.The magnetic directional motion and shape memory of PLA/TBC/Fe₃O₄microspheres were verified by light microscopy and scanning electron microscopy,and the biosafety of PLA/TBC/Fe₃O₄ microspheres was verified by in vivo/ex vivo cytotoxicity assay.PLA/TBC/Fe₃O₄ microspheres with a magnetic particle content of15 wt.%had the ability to move in a directional manner under an applied magnetic field and shape memory under a heat source of 40°C.In addition,PLA/TBC/Fe₃O₄microspheres with a concentration of 500μL/mg had a certain promotion effect on cell proliferation and had a good biosafety.The ellipsoidal-shaped PLA/TBC/Fe₃O₄microspheres could penetrate 29μm into the dentin tubules under the action of an applied magnetic field and revert to spherical shape to achieve blockage under heat source at 40°C.The entry rate of PLA/TBC/Fe₃O₄ microspheres with shape memory was 85.41±7.11%,and the blockage rate was 93.33±2.82%.更多还原