Amorphous PLLA

Fig. 8. Normalized tissue growth in amorphous PLLA devices of different pore sizes ( 500 pm ( ) 179 pm (O) and 91 pm (A)) as a function of implantation time [45], The error bars designate means + range of two sections...

Figure 11.5 DSC thermograms of amorphous PLLA and PDLLA at a heating rate of 10°C/min.

Figure 8.22 Weight loss of crystallized PLLA (PLLA-C), amorphous PLLA (PLLA-A), R-P(3HB), and PCL exposed to seawater at 25 °C[285]. (Reproduced with permission from ref 12851 Copyright Elsevier, 2002.)...

Fig. 13.12. Schematic representation of chain folding and domain spacing of the amorphous PCL block (top), amorphous PLLA block (middle) and crystalline PLLA block (bottom) for (a) PLLA-6-PCL (high l / ) and (b) PLLA-6-PCL (low M ) at 110" C and 140°C. Taken from [29]...

Li et al found this mechanism in initially amorphous PLLA samples, in which hydrolytic chain scission resulted in lower molecular weight and absorbed water acted as a plasticiser, both resulting in increased chain mobihty, and the ability of the chain segments to crystallise, which in turn improved... 

TABLE 8.1 Infrared Spectroscopy Data Peak Band Assignments for Semicrystalline and Amorphous PLLA Infrared and Raman Spectra... 

FIGURE 9.1 Differential scanning calorimetry thermograms of amorphous PLLA and PDLLA (heating rate 10°C/min). 

Vicat penetration is much more influenced by PLA crystallinity. In the case of PDLLA and amorphous PLLA, Vicat penetration values of 52-53°C and 59-60°C, respectively, were reported. Also these values are very near to the Tg of the polymers. On the other hand, crystalline PLLA presents a very different behavior, with values of 157-165°C. This marked difference in Vicat penetration measurements is related to the contribution of crystallinity to thermomechanical properties of this material at a microscopic level [2,7]. 

FIGURE 21.13 Mn change of amorphous PLLA having high and low molecular weights (PLLA(H) and PLLA(L), respectively), P(LLA-co-DLA) (77/23), poly(L-lactide-co-glycolide) (P(LLA-C( -GA)) (81/19), and poly(L-lactide-co-8-caprolactone) (P(LLA-co-CL)) (82/18) with respect to hydrolytic degradation in a phosphate-buffered solution [39, 40, 159]. 

To study the enzymatic degradation of the free amorphous region, completely amorphous PLLA thin film was prepared (see Section 22.3.2), and the erosion rate was directly monitored by using QCM in the nanogram per square centimeter regime [74]. The enzymatic erosion rate was dependent on the concentration of proteinase K, and the thin amorphous film of lOOnm thickness was completely hydrolyzed in 20 min when the concentration of the enzyme was >100 qg/mL. During the course of enzymatic degradation, even if the enzyme solution was replaced with a buffer solution (i.e.. 

PHB crystalline bands observed were the C—O stretching band at 1720cm , the C—O—C stretching band at 1275 cra , and the band at 1261 cm that was due to the coupling of C—O—C stretching and C—H deformation modes. These bands were clearly identified in the spectra shown in Figure 20.25a and b. The spectra including amorphous PLLA bands at 1745 cm were obtained in some... 

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