Polymer, amorphous purification

To a synthetic chemist the concept of a polymer is rather different. The term is often used to describe molecules formed from quite small numbers of monomers units but which resist crystallization and purification owing to the range of chain lengths present. Such materials will normally form brittle solids which are either amorphous or have a low level of crystalline order. 

PLA is a crystal clear, transparent material when amorphous that becomes hazier the higher the crystallinity. Crystallized material is opaque. When producing lactide, meso-lactide is formed as a by-product. It is difficult to separate the meso-lactide from the L-lactide in the purification step. When polymerizing L-lactide with small contents of meso-lactide a co-polymer is formed. Increasing meso-lactide leads to decreasing crystallinity. With more than 10-15% meso-lactide the polymer is amorphous. 

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