Poly(vinylimidazole) brushes as anchoring strategy to build hybrids ZIF-8/polymeric films

JUAN A. ALLEGRETTO; JUAN M GIUSSI; MATÍAS RAFTI; SERGIO MOYA; OMAR AZZARONI; AGUSTÍN IBORRA

San Sebastian

Workshop; Workshop on Self-assembly and Hierarchical Materials in biomedicine: Drug Delivery, Tissue Engineering, Sensing and Safety Issues; 2018

CIC BIOMAGUNE

ZIF-8 (Zeolitic Imidazolate Framework), a hydrophobic microporous MOF, constituted by Zn2+ clusters coordinated with 2-methylimidazole ions (mIm-), have been reach a wide range of applications, ranging from gas sensors to drug/cargo delivery platforms during the last years. In this work, we shown how to use Poly(vinylimidazole) (PvIm) brushes to direct the growth of ZIF-8 films and control it by adjusting brush grafting density (BGD). The BGD was controlled by bonding covalently an ATRP initiator (α-bromoisobutyryl bromide) (Br-iBuBr) on APTES grafted SiO2 surfaces together with an inert silane as Trietoxy(ethil)silane (TEES) in different amounts (Two-steps grafting). Also, we have modified APTES with Br-iBuBr ex-situ to use it to graft SiO2 surfaces (One-step grafting). TEES was added at 0-5-50-100% amounts relative to APTES (or BrPTES). PvIm brushes were synthesized via ATRP. ZIF-8 films were synthesized under stoichiometric conditions from 25 mM Zn(NO3)2·6H2O and 50 mM 2-methylimidazole (HmIm) solutions, both in anhydrous methanol. XPS experiments shown a successfully surface modification and later ZIF-8 growth. QCM experiments reveal the differences on that growth according to the BGD, while AFM experiments shown a continuous ZIF-8 film over the PvIm from Two-steps grafting surfaces while isolated crystallites growth onto those PvIm synthesized from One-step grafted surfaces. In addition, crystallites size increases as decrease the BGD. The found differences indicates that brush density was different for each condition and that it has an impact on ZIF-8 films growth.