title: Porosity and surface properites of SBA-15 with grafted PNIPAAM: a water sorption calorimetry study.
abstract: Mesoporous silica SBA-15 was modified in a three-step process to obtain a material with poly-N-isopropylacrylamide (PNIPAAM) grafted onto the inner pore surface. Water sorption calorimetry was implemented to characterize the materials obtained after each step regarding the porosity and surface properties. The modification process was carried out by (i) increasing the number of surface silanol groups, (ii) grafting 1-(trichlorosilyl)-2-(m-/p-(chloromethylphenyl) ethane, acting as an anchor for (iii) the polymerization of N-isopropylacrylamide. Water sorption isotherms and the enthalpy of hydration are presented. Pore size distributions were calculated on the basis of the water sorption isotherms by applying the BJH model. Complementary measurements with nitrogen sorption and small-angle X-ray diffraction are presented. The increase in the number of surface silanol groups occurs mainly in the intrawall pores, the anchor is mainly located in the intrawall pores, and the intrawall pore volume is absent after the surface grafting of PNIPAAM. Hence, PNIPAAM seals off the intrawall pores. Water sorption isotherms directly detect the presence of intrawall porosity. Pore size distributions can be calculated from the isotherms. Furthermore, the technique provides information regarding the hydration capability (i.e., wettability of different chemical surfaces) and thermodynamic information.
authors.affiliation: Physical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden. nina.reichhardt@fkem1.lu.se
authors.forename: N V
authors.initials: NV
authors.lastname: Reichhardt
authors.forename: T
authors.initials: T
authors.lastname: Nylander
authors.forename: B
authors.initials: B
authors.lastname: Klösgen
authors.forename: V
authors.initials: V
authors.lastname: Alfredsson
authors.forename: V
authors.initials: V
authors.lastname: Kocherbitov
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D002151:Calorimetry / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; C509969:SBA-15; D014867:Water; C052970:poly-N-isopropylacrylamide; D012822:Silicon Dioxide