Copolymers degradation model

Desired degradation rates for copolymers can be achieved by simply choosing different copolymer ratios for different homopolymers, PLA and PGA for example. The copolymer degradation rate and copolymer ratio follows some complicated relations. In the molecular models, highly complex chemical structures of copolymers can be represented by carefully distributing different coloured beads with corresponding hydrolysis rates on one polymer chain based a certain copolymer ratio. Polymer characteristics, such as the initial MWD, degree of aystallinity and copolymer ratio, are all considered as input data in a molecular model. The model is then used to study the effect of every mechanism for both homopolymer systems and copolymer systems. 

The copolymer ratio of a polymer system greatly alters its degradation rates. Poly(DL-lactic acid) (PDLA) and PGA are the most used linear polymers, due to well-established biocompatibilities. It is possible to achieve a desired degradation rate by using different copolymer ratio of PGA and PDLA. In this section, we use a KMC degradation model for a PLGA copolymer system in order to study its innate... 

In all types of PHAs, P4HB is of the most interest because it was used in the degradable scaffold that resulted in the first successful demonstration of a tissue-engineered tri-leaflet heart valve in a sheep animal model. Its copolymers with PHB and polyhydroxyoctanoate (PHO) are also promising in tissue engineering because of their nontoxic degradation products, stability in tissue culmre media, and the potential to tailor the mechanical and degradation properties to match soft tissue. 

P. Scanducci de Freitas, U. Scherf, M. Collon, and E.J.W. List, (9,9-Dialkylfluorene- co-fluorenone) Copolymers containing low fluorenone fractions as model systems for degradation-induced changes in polyfluorene-type semiconducting materials, e-Polymers, Abstr. No. 009, 2002. 

The relationship between the structure of the oligopeptide sequences and the rate of enzymatically catalyzed release of a drug or drug model was studied in detail. Over 50 different oligopeptide sequences were introduced into HPMA copolymers and their degradability by different enzymes studied. First, model enzymes, chymotrypsin [235, 238,239, 243,244], trypsin [245], and papain... 

Silvestri S, Gabrielson G, Wu LL (1991) Effect of terminal block on the microfluidization induced degradation of model ABA block copolymer. Int J Pharm 71 65-71... 

Earlier, tertiary chlorine was generally considered to be less reactive than internal double bonds. This was based on experiments with low molecular weight model substances, see e.g. ref. 45. However, using copolymers between vinyl chloride and 2-chloro-propene, Berens (46) stated that the presence of 1-2 tertiary chlorine per 1000 VC per se would account for the thermal lability observed in ordinary PVC. Furthermore, our previous investigation indicated that the thermal reactivity of internal allylic chlorine is of the same order as that of tertiary chlorine (8). We, therefore, consider it justifiable to use the total content of labile chlorine atoms. As shown in Figure 10, there is a very good relation between the rate of dehydrochlorination and the amount of labile chlorine obtained in this way. For comparison, it can be mentioned that the degradation rate of commercial samples is found in the interval 1.5-3.5 10 %... 

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