Biodegradable polymers thermal treatment

Biodegradable polymers Effect of thermal treatment on the physicomechanical and dissolution properties of compacts... 

Despite successful results from in vitro studies, however, the clinical applications of systems that are based on polyNlPAAm may be limited, becanse poly-NIPAAm is nondegradable and insoluble. In addition, a major problem of polyNIPAAm-based drug deUvery systems is that thermal treatment is required for controlled destabilization of the micelles and concurrent drug release, which is not always feasible in clinical situations. Therefore, to overcome the disadvantages of polyNIPAAm, controlled biodegradable systems that use polyester block copolymers as thermosensitive polymers have been investigated. 

Solvent casting and particulate leaching (SC/PL) is a simple and commonly used method for fabricating scaffolds for tissue engineering. With an appropriate thermal treatment, porous constructs of synthetic biodegradable polymers can be prepared with specific porosity, surfaceivolume ratio, pore size and crystallinity for different applications. This method involves mixing water-soluble salt (e.g. sodium chloride, sodium citrate) particles into a polymer solution. The mixture is then cast into the mould of the desired shape. After the solvent is removed by evaporation or lyophilization, the salt particles are leached out to obtain a porous structure with the pore shape limited to the cubic crystal shape of the salt. Removal of soluble particles from the interior of a polymer matrix is difficult and limits the thickness of the films prepared to ca. 2 mm [293]. 

Though PAC is relatively non-toxic and environmentally benign, it is not biodegradable. This causes a disposal problem in waste water treatment facilities, where the PAC must be removed and land filled. The problem for it s disposal has been solved by Donlar Corporation, which has developed a method for the production of TPA (thermal polyaspartate), a biodegerable alternative to. PAC. The Donlar s synthesis consists of heating the aspartic acid followed by hydrolysing the formed succinimide polymer with aqueous base (Scheme 114). 

Yang, S. Y. and Huang C. Y. Plasma treatment for enhancing mechanical and thermal properties of biodegradable PVA/starch blends. Journal of Applied Polymer Science, 109, 2452-2459 (2008). 

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