Wang Shanfeng, Lu Lichun, Yaszemski Michael J
Tissue Engineering and Polymeric Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, Minnesota 55905, USA.
Biomacromolecules. 2006 Jun;7(6):1976-82. doi: 10.1021/bm060096a.
Poly(propylene fumarate) (PPF) is an important biodegradable and cross-linkable polymer designed for bone-tissue-engineering applications. For the first time we report the extensive characterization of this biomaterial including molecular weight dependences of physical properties such as glass transition temperature Tg, thermal degradation temperature Td, density rho, melt viscosity eta0, hydrodynamic radius RH, and intrinsic viscosity [eta]. The temperature dependence of eta0 changes progressively with molecular weight, whereas it can be unified when the temperature is normalized to Tg. The plateau modulus and entanglement molecular weight Me have been obtained from the rheological master curves. A variety of chain microstructure parameters such as the Mark-Houwink-Sakurada constants K and alpha, characteristic ratio Cinfinity, unperturbed chain dimension r0(2)/M, packing lengthp, Kuhn length b, and tube diameter a have been deduced. Further correlation between the microstructure and macroscopic physical properties has been discussed in light of recent progress in polymer dynamics to supply a better understanding about this unsaturated polyester to advance its biomedical uses. The molecular weight dependence of Tg for six polymer species including PPF has been summarized to support that Me is irrelevant for the finite length effect on the glass transition, whereas surprisingly these polymers can be divided into two groups when their normalized Tg is plotted simply against Mw to indicate the deciding roles of inherent chain properties such as chain fragility, intermolecular cooperativity, and chain end mobility.
聚富马酸丙二醇酯（PPF）是一种重要的可生物降解且可交联的聚合物，专为骨组织工程应用而设计。我们首次报道了对这种生物材料的全面表征，包括玻璃化转变温度Tg、热降解温度Td、密度ρ、熔体粘度η0、流体力学半径RH和特性粘度[η]等物理性质对分子量的依赖性。η0的温度依赖性随分子量逐渐变化，而当温度归一化为Tg时则可以统一。通过流变主曲线获得了平台模量和缠结分子量Me。推导了各种链微观结构参数，如马克-豪温克-樱田常数K和α、特征比C∞、无扰链尺寸r0(2)/M、堆积长度p、库恩长度b和管径a。根据聚合物动力学的最新进展，讨论了微观结构与宏观物理性质之间的进一步相关性，以便更好地理解这种不饱和聚酯，从而推进其生物医学应用。总结了包括PPF在内的六种聚合物的Tg对分子量的依赖性，以支持Me与玻璃化转变的有限长度效应无关，然而，令人惊讶的是，当将它们的归一化Tg简单地与Mw作图时，这些聚合物可分为两组，这表明链脆性、分子间协同性和链端迁移率等固有链性质起决定性作用。
