Anisotropic crystal growth in aerosil/polymethylmethacrylate systems dispersed in dimethacrylate monomers

Complex organized crystals were shown to grow within the settled phase composed of aggregated aerosil/polymethylmethacrylate or aerosil/poly(cetyl vinyl ether–maleic anhydride) resulting from the supply of the corresponding homopolymer or the alternated copolymer to the aerosil initially dispersed in a mixture of dimethacrylate monomers. The basic suspending phase was realized by mixing 1,3-butanediol dimethacrylate and bisphenol A dimethacrylate. The crystal nucleation and growth were both extremely slow processes that developed over months. Small and large crystals were realized usually displaying the shape of hexagonal platelets. The dose of polymer initially supplied to the system exerted a structuring role in the crystalline organization. DCS determinations showed the enthalpy of fusion to depend on the polymer dose and molecular weight. AFM showed the basal and lateral phases to grow with developing steps of two different thicknesses. The monomer ordering was evidenced by the fact that the polymerization shrinkage only affected the sequence of monomers lying parallel to the basal phases, the polymerization of monomers along the perpendicular axis being prevented from any shrinkage.

Crystal hexagonal platelets nucleate and grow within the settled phase resulting from the supply of polymer to aerosil particles dispersed in a mixture of 1,3-butanediol dimethacrylate and bisphenol A dimethacrylate.Figure optionsDownload as PowerPoint slide