ИСТИНА

Poly(lactic acid), PLA, is a biocompatible and biodegradable aliphatic polyester. The raw materials for its production are renewable resources of vegetable origin, such as corn and sugar cane. The most promising area of application is the medicine, namely in transplantation (implant shell), surgery (suture) and as containers for long-acting medications. However, one of the distinguishing characteristics of this polymer is its insolubility in water and water-alcohol mixtures, which complicates the introduction of any thermally unstable fillers (e.g., drugs) in this type of matrix. One of the solutions to this problem is the creation of the porous structure, which can be quite easily filled with a necessary component. Porous PLA matrix is suggested to obtain using the fundamental property of glassy and semi-crystalline polymers - crazing in adsorption-active fluids. This process allows to create rather regular porous structure with precisely controlled parameters (porosity of 60 vol%, pore diameter ~10 nm) and fill it with the objective filler. The purpose of this operation is to learn the process of solvent-crazing in industrial amorphous films of poly-L-lactide (Mw=200 kDa, thickness 300 mcm) in different fluids (aliphatic alcohols, water-ethanol mixtures, hydrocarbons, etc). In this work, it is shown for the first time that the deformability of amorphous PLA film considerably increases in the presence of liquid adsorption-active media: from 15% in air to 500% in ethanol. Large plastic deformations are developed by the crazing mechanism and accompanied by the formation of a fibrillar–porous structure with diameter of pores and fibrils of about 20 nm. The tension to high degrees of deformation (more than 300%) in alcohols results in intense crystallization of PLA films.