STRUCTURAL-ANALYSIS OF PPX PREPARED BY VAPOR-PHASE PYROLYSIS OF [2.2]PARACYCLOPHANE

Poly(p-xylylene) (PPX) was prepared by vapor phase pyrolysis of [2.2]p aracyclophane following the procedure of Gorham. PPX was obtained in d ifferent crystalline modifications by dry annealing, dissolution and r eprecipitation under different conditions. These samples were analyzed by WAXS and C-13 CP-MAS NMR spectroscopy. Clear evidence was found th at the presence of different crystalline modifications is responsible for the unexpected C-13 CP-MAS NMR spectrum as observed for as-polymer ized PPX. An attempt was made to explain the differences observed in t he C-13 CP-MAS NMR spectra of different crystalline modifications by d ifferent chemical environments utilizing simulations of the crystal un it cells.