Synthesis and characterization of POSS-(PAA)8 star copolymers and GICs for dental applications

Publication date: Available online 19 February 2016
Source:Dental Materials
Author(s): Christina Zelmer, David K. Wang, Imelda Keen, David J.T. Hill, Anne L. Symons, Laurence J. Walsh, Firas Rasoul
ObjectiveTo investigate the application of a new type of multiarm polymer resins in the formulation of Glass Ionic Cements.MethodsA series of star copolymers of t-butyl acrylate has been prepared by ATRP using a multiarm POSS-Br8 initiator. The resulting POSS-co-t-butyl acrylate star copolymers with eight arms were subsequently hydrolysed by trifluoroacetic acid to produce the corresponding POSS-co-acrylic acid star copolymers. All of the copolymers have been characterized by ¹H and ¹³C NMR and FTIR spectroscopies and TGA/DSC. The as-prepared star copolymers were mixed with the glass powder from Fuji IX GP to produce the GIC samples for compression testing.ResultsThe new type of multiarm polymer resins have been shown to have narrow molecular weight distributions and thermal properties of the acrylic acid copolymers are similar to that of poly(acrylic acid), with a two stage degradation profile involving transitions at ≈140°C and 250°C, corresponding to anhydride formation and loss of carbon dioxide, respectively. In aqueous solution the POSS-co-acrylic acid copolymers form aggregates with ≈33nm dimensions. When aqueous solutions of POSS-(PAA)8 are mixed with a glass powder, a rigid glass ionomer cement, GIC, is formed with a maximum compressive stress significantly greater than that for a linear PAA GIC of a comparable polymer molecular weight.SignificanceTherefore, these POSS-(PAA)8 copolymers demonstrate the potential for the application of well characterized star copolymers in the future development of new GICs as dental materials.

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