BRANCHED BPA POLYCARBONATES WITH HIGH SHEAR SENSITIVITY FROM RING-OPENING POLYMERIZATION OF CYCLIC CARBONATES

Branched BPA polycarbonates with high shear sensitivity (i.e. having complex melt viscosity ratios as high as 8.0 or even 10.0) were prepared by ring opening polymerization of cyclic oligomeric BPA carbonates in the melt (at 275 C) with various branching agents [e.g. 1,3,5-tris(chloromethyl)-2,4,6-trimethylbenzene, bis(2,4-dihydroxyphenyl) sulfide, and 1,1,1-tris(4-hydroxyphenyl)ethane]. Furthermore, it was determined that the shear sensitivity is directly related to the branching agent level and inversely related to the level of initiator used in the ring-opening polymerization.