Dr Lucia Scotti, Dr Mike Jenkins, Dr Hector Basoalto
University of Birmingham
- Polymers crystallise in spherulites composed by lamellae of semi crystalline material alternating with amorphous regions;
- The size, morphology and crystallinity of the spherulites influence the polymer properties;
- The radius of spherulites range from lateral μm to cm;
- The lamellae are very thin compared to the fully extended chain: usually 10 nm.
- A fully extended chain requires an enormous decrease of entropy, so it can be obtained only under particular conditions;
- The folding back and forth of polymer chains requires a release of a part of the entropy;
- The folded chains are metastable phases: the free energy of the folded-surfaces is much higher than the lateral surface;
- These crystals are stabilised by spontaneous thickening processes
Fig.1: Schematic representation of lamellae composed of folded chains and amorphous regions in spherulite.
Fig.2: Schematic representation of a polymer chain phase