Generalization on Crystallization

• If it is to crystallize, a homopolymer must have an ordered chain microstructure. For example, if it is a vinyl polymer, the tacticity matters. The chain should be isotactic or syndiotactic, but not atactic.
• If the chain is a copolymer, there should be a regular arrangement (block or alternating) of units.
• If the disordered state has a large number of conformations of low energy, as is seen in poly(1,4-cis-isoprene), the large conformational entropy of the disordered state will resist crystallization.
  • But crystallization of poly(1,4-cis-isoprene) can be achieved on stretching, which reduces the conformational entropy of the disordered state.
• Crystallization can be prevented by fast cooling (quenching) from the melt to a temperature below T_g.

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