Case Study Of Template-induced And Additive-induced Crystallization

The induction of templates or additives is one of the most important methods for the manipulation on crystallization.However,because of the lack of effective experimental characterization,the understanding on induction mechanism is still poor.In this study,a method combining experiment,characterization and molecule simulation is established to study the process and mechanisms of template-or additive-induced crystallization of selected model system.Induction time statistics,detection of the concentration of paracetamol(APAP)near the surface of membrane,and PXRD were employed to characterize the induction of nylon 66(PA66),polyester(PET)and polypropylene(PP)membrane on the heterogeneous nucleation and growth of APAP.The results show that PA66 was the most effective template among the three polymers,which significantly promoted preferential orientation of APAP crystals along(0 0 1)facet,while PET also promoted preferential orientation along both(0 0 1)or(2 0-1)facet.PP was the weakest template and had less effect on the preferential orientation of APAP crystals.Molecule simulation was conducted to analyze the interaction mechanism between APAP and different polymers.The results show that the interaction between PA66 and APAP was strongest among the three polymers.Also,the APAP crystals tend to preferentially orient along(0 0 1)facet on surface of PA66,while tend to preferentially orient along(0 0 1)and(2 0-1)facet on the surface of PET.However,the interaction of PP with APAP was the weakest.These simulation results were consistent with the experimental characterization results,which demonstrated the induction mechanism of different templates.MD simulation was also employed to further study the effect of acetanilide(ACET),acetaminophen(APAP)and p-methyl acetanilide(PMAA)on the crystal growth on MP.The results indicated that ACET,APAP and PMAA was easy to be adsorbed to the solvated interface of(-1 1 0),(0 2 1)and(0 2 0)facets of methyl paraben(MP),respectively,while was difficult to be adsorbed to the solvated interface of(1 1-1),(-1 1 1)and(1 1-1),respectively.This study provides a better guidance on template-or additive-induced crystallization.