Regulating Nucleation Kinetics through Molecular Interactions at the Polymer-Solute Interface

Heterogeneous nucleation is ubiquitous both in nature and in industrial practice; therefore, the ability to inhibit or enhance the kinetics of a crystallization process is essential in many scientific and technological areas. In order to better understand the role of surface functionality in regulating the nucleation rate, six commercially available polymers have been used as heteronucleants of acetaminophen (ACM) molecules: polydimethylsiloxane (PDMS) with siloxane functional groups Si-O-Si forming the backbone of silicones, partially fluorinated elastomer polyvinylidenedifluoride (PVDF), polystyrene (PS) having weak electron-donor phenyl rings, poly(n-buthyl methacrylate) (PnBMA) showing ester functionality, polyimide (PI) that includes both hydrogen-bond acceptor imide functionality and carbonyl groups, ethylene/acrylic acid (EAA) copolymer with carboxyl moiety. Experimental results from induction time statistics, van Oss-Chaudhury-Good model of surface energetics, and powder X-ray diffraction (PXRD) analysis showed that polymeric interfaces promoting specific acid-base interactions and directionally ordered reorganization of molecules led to enhanced nucleation kinetics, while the formation of nuclei was retarded on hydrophobic films that did not induce preferential orientations of the crystalline facets.