Spectroscopic evaluation, thermal, and thermomechanical characterization of poly(glycerol-sebacate) with variations in curing temperatures and durations
Spectroscopic evaluation, thermal, and thermomechanical characterization of poly(glycerol-sebacate) with variations in curing temperatures and durations
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DOI：
10.1007/s10853-010-4259-0
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发表时间：
2010-05-01
影响因子：
4.5
通讯作者：
Coulter, John P.
中科院分区：
文献类型：
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作者：
Jaafar, Israd H.;Ammar, Mohamed M.;Coulter, John P.
具有与体内发现的那些相似的物理、机械和化学性质的新型材料为构建用于组织工程和治疗应用的人工微环境提供了潜在的平台。聚（甘油-癸二酸酯）（PGS）[1]是一种通过甘油和癸二酸缩聚合成的坚韧弹性体，在仿生材料领域显示出前景。PGS具有生物相容性和生物可降解性，在常见软组织范围内具有可调的机械性能。研究发现，PGS在机械性能、生物降解特性以及细胞反应和形态方面上级聚（L-乳酸-乙醇酸）（PLGA）[1，2]，后者是生物界面研究中常用的聚合物。PGS的表征研究着眼于其机械特性[3]、通过差示扫描量热法（DSC）进行的热分析[1，4]、通过傅里叶变换红外（FTIR）光谱进行的分子键合方案[1，4]、体外和体内降解特性[1，2]、生物相容性[1，5，6]、溶胀行为[2，3]、和形状记忆效应[4]。然而，这些性能作为固化参数的函数的受控宽范围研究尚未报道，限制了性能“可调性”的标准化。本研究旨在通过研究固化时间表对其物理和机械性能的影响来扩展这方面的知识。预聚物和聚合物固化参数的优化和标准化将使研究人员能够针对特定应用“调整”PGS的仿生特性。采用衰减全反射-傅里叶变换红外光谱（ATR-FTIR）、DSC、动态力学分析（DMA）和平衡拉伸试验对各种PGS样品进行了表征。我们在这里报告说，PGS是一种半结晶弹性体，在35 ℃以上完全无定形，预聚物的最大熔融转变温度约为-25至35 ℃。我们还表明，在这种材料中的交联度取决于固化温度和固化时间，并且该参数可以从ATR-FTIR光谱数据和材料弹性的变化中推断。一个特定的ATRFTIR光谱峰和材料的平衡模量之间的关系也已被推导出来。然而，该研究也遇到了意想不到的数据，其中PGS表现出不改变的玻璃化转变温度（Tg），以及随着交联度的增加而在Tg下提高的阻尼能力。我们还对找到最佳的预聚物合成和固化时间感兴趣。这些原因为我们提供了对PGS进行进一步表征的动力。PGS预聚物的合成是从已建立的方法[1]改编的。简言之，等摩尔（1：1）将一定量的无水甘油（Sigma-Aldrich）和癸二酸（Sigma-Aldrich）在部分浸入加热的硅酮浴中的气密玻璃罐中混合。在氮气流下将混合物逐渐加热至120 ℃，并用转子以50 rpm搅拌24小时.然后停止气流并施加真空（在-20kPa下）48小时。缩聚产生高粘性的预聚物。PGS样品通过在真空烘箱（在_20kPa）中在设定温度下固化预聚物来获得。
Novel materials possessing physical, mechanical, and chemical properties similar to those found in vivo provide a potential platform in building artificial microenvironments for tissue engineering and therapeutic applications. Poly (glycerol-sebacate)(PGS)[1], a tough elastomer that is synthesized through the polycondensation of glycerol and sebacic acid, shows promise in the field of biomimetic materials. PGS is both biocompatible and biodegradable, with tunable mechanical properties within the range of common soft tissue. Studies have found that PGS is superior, in terms of mechanical properties, biodegradation characteristics, as well as cell response and morphology to poly (L-lactic–glycolic acid)(PLGA)[1, 2], a commonly used polymer in biointerface studies. Characterization studies on PGS have looked at its mechanical characteristics [3], thermal analysis via differential scanning calorimetry (DSC)[1, 4], molecular bonding schemes via Fourier transform infrared (FTIR) spectroscopy [1, 4], in vitro as well as in vivo degradation characteristics [1, 2], biocompatibility [1, 5, 6], swelling behavior [2, 3], and shape-memory effect [4]. However, a controlled widerange study of these properties as a function of curing parameters has yet to be reported, limiting the standardization of property ‘‘tunability’’. The present study aims to expand on this body of knowledge by examining the effect of cure schedule on both its physical and mechanical properties. The optimization and standardization of the pre-polymer and polymeric curing parameters will allow researchers to ‘‘tune’’the biomimetic properties of PGS for a given application. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), DSC, dynamic mechanical analysis (DMA), and equilibrium tensile testing were used to characterize various PGS samples. We report here that PGS is a semi-crystalline elastomer that is fully amorphous above 35 C with the largest melting transition temperature being approximately-25 to 35 C for the pre-polymer. We also show that the degree of crosslinking in this material is dependent on cure temperature and duration of cure, and that this parameter can be inferred from changes in ATR-FTIR spectral data and material elasticity. A relationship between a specific ATRFTIR spectral peak and material equilibrium modulus has also been derived. However, the investigation also encountered unexpected data where PGS exhibits a glass transition temperature (Tg) that does not change, and a heightened damping capacity at Tg with increasing degrees of crosslinking. We were also interested in finding the optimum pre-polymer synthesis and cure times. These reasons provided the impetus for us to conduct further characterization on PGS.The PGS pre-polymer synthesis was adapted from established methods [1]. Briefly, equimolar (1: 1) amounts of anhydrous glycerol (Sigma–Aldrich) and sebacic acid (Sigma–Aldrich) were mixed in an airtight glass jar that was partially immersed in a heated silicone bath. The mixture was gradually heated to 120 C under nitrogen gas flow and stirred with a rotor at 50 rpm for 24 h. The gas flow was then stopped and vacuum (at-20 kPa) was applied for 48 h. Polycondensation results in a highly viscous pre-polymer. PGS samples were obtained by curing the pre-polymer in a vacuum oven (at-20 kPa) at set