Sabino Marcos A, Albuerne Julio, Müller Alejandro J, Brisson Joseé, Prud'homme Robert E
Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela.
Biomacromolecules. 2004 Mar-Apr;5(2):358-70. doi: 10.1021/bm034367i.
We have studied the hydrolytic degradation of high molecular weight poly(p-dioxanone), PPDX, sutures. The samples were degraded either in distilled water or in a phosphate buffer at 37 degrees C, and the starting viscosity-average molecular weight was 130 kg/mol. The hydrolytic degradation of PPDX occurs in an approximate two stage process where the amorphous regions of the sample are attacked faster than the crystalline regions of the sample. The changes experienced by the samples as degradation proceeded were successfully monitored by viscosimetry, differential scanning calorimetry (DSC), weight loss, pH changes, and scanning electron microscopy (SEM). Polarized optical microscopy (POM) observations performed on PPDX films revealed that PPDX crystallizes in spherulites whose detailed morphology depends on the supercooling employed during isothermal crystallization. Changes in the spherulitic morphology as molecular weight is reduced are only pronounced when the molecular weight is equal or lower than 8 kg/mol. The dependence of lamellar thickness as a function of isothermal crystallization temperature was examined by atomic force microscopy (AFM) in thin films of PPDX together with melting point data obtained by DSC. Through the use of the Thomson-Gibbs equation, we obtained a value of 166 erg/cm2 for the fold surface free energy of PPDX. This value is in the same range as those obtained previously for similar linear polyesters. The lamellar thickness, as well as the melting point, was found to have a small decreasing dependence with the molecular weight of the samples.
我们研究了高分子量聚对二氧环己酮（PPDX）缝线的水解降解。样品在37℃的蒸馏水或磷酸盐缓冲液中降解，起始粘均分子量为130 kg/mol。PPDX的水解降解过程大致分为两个阶段，其中样品的无定形区域比结晶区域更容易受到侵蚀。随着降解的进行，通过粘度测定法、差示扫描量热法（DSC）、失重、pH值变化和扫描电子显微镜（SEM）成功监测了样品所经历的变化。对PPDX薄膜进行的偏光光学显微镜（POM）观察表明，PPDX以球晶形式结晶，其详细形态取决于等温结晶过程中采用的过冷度。只有当分子量等于或低于8 kg/mol时，随着分子量降低球晶形态的变化才会明显。通过原子力显微镜（AFM）在PPDX薄膜中研究了片晶厚度与等温结晶温度的函数关系，并结合DSC获得的熔点数据。通过使用汤姆森-吉布斯方程，我们得到PPDX的折叠表面自由能值为166 erg/cm²。该值与先前为类似线性聚酯获得的值在同一范围内。发现片晶厚度以及熔点对样品分子量的依赖性较小。
