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Polymers are composed of long molecular chains which form irregular, entangled coils in the melt. Some polymers retain such a disordered structure upon freezing and readily convert into amorphous solids. In other polymers, the chains rearrange upon freezing and form partly ordered regions with a typical size of the order 1 micrometer. [3]
In polymer physics, spherulites (from Greek sphaira = ball and lithos = stone) are spherical semicrystalline regions inside non-branched linear polymers. Their formation is associated with crystallization of polymers from the melt and is controlled by several parameters such as the number of nucleation sites, structure of the polymer molecules, cooling rate, etc. Depending on those parameters ...
Polymer morphology is a microscale property that is largely dictated by the amorphous or crystalline portions of the polymer chains and their influence on each other. Microscopy techniques are especially useful in determining these microscale properties, as the domains created by the polymer morphology are large enough to be viewed using modern ...
Polymers have both a melting temperature T m and a glass transition temperature T g. Above the T m, the polymer chains lose their molecular ordering and exhibit reptation, or mobility. Below the T m, but still above the T g, the polymer chains lose some of their long-range mobility and can form either crystalline or amorphous regions. In this ...
Polyamorphism is also an important area in pharmaceutical science. The amorphous form of a drug typically has much better aqueous solubility (compared to the analogous crystalline form) but the actual local structure in an amorphous pharmaceutical can be different, depending on the method used to form the amorphous phase.
Polymers that are formed by free-radical mechanisms such as polyvinyl chloride are usually atactic. [citation needed] Due to their random nature atactic polymers are usually amorphous. [citation needed] In hemi-isotactic macromolecules every other repeat unit has a random substituent. [citation needed]
The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. [1] Examples of amorphous solids include glasses, metallic glasses , and certain types of plastics and polymers .
Disordered polymers: In the solid state, atactic polymers, polymers with a high degree of branching and random copolymers form amorphous (i.e. glassy structures). [45] In melt and solution, polymers tend to form a constantly changing "statistical cluster", see freely-jointed-chain model .