Owing to the presence of two phenylene groups in the constitutional repeating unit,bisphenol-A polycarbonate (BAPC) has too rigid chain-segments,which result in its extremely slow crystallization.In this work,three types of crystallization-rate enhancers reported in the literature have been reviewed and commented for BAPC,including nucleating agents (NAs),crystal-growth accelerators (CGAs),and nucleation-crystal-growth coupled modifiers (NA-CGAs),and a new concept of "ion-aggregation induced nucleation (IAIN)",which is distinct in mechanism from heterogeneous nucleation (HN),has been proposed,i.e.,a process of translocation of an NA's ion pairs via exchange reaction to BAPC chain ends,followed by monochelic or telechelic ion-aggregation,due to electrostatic attractions,to trigger close packing of covalently attached chain-segments in the coronas of the ionic aggregates,thus inducing crystalline nucleation of the BAPC.The NAs for BAPC include inorganic fillers,organic small-molecules,organic polymers,etc.,the former of which belongs to HN,and the latter two of which assume either HN or IAIN,contingent upon whether there are exchangeable ion pairs.The CGAs comprise organic solvents,supercritical CO2,ester plasticizers,liquid-crystalline smallmolecules,flexible polymers,etc.,all of which accelerate the crystal growth invariably through decreasing the chain intersegmental interactions of BAPC.The NA-CGAs are mixtures of NA and CGA that accelerate jointly the crystallization of BAPC.Nevertheless,the crystallization-rate enhancement for BAPC has still been insufficient within a time scale of practical melt-processing;to address this issue,HN-IAIN-CGA coupled ternary modifiers are becoming one of the most promising approaches to the maximal improvement in BAPC crystallization.
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