Adsorption and Migration of Poly(Vinyl Pyrrolidone) at a Fumed Silica Surface

Abstract

A series of poly(vinyl pyrrolidone) (PVP)/fumed silica powder samples were studied using adsorption, FT-IR and AFM methods. Mild treatment (293 K for several hours) of PVP/A-300 powder with an added additional portion of A-300 in a glass reactor (2 dm 3 ) using a mixer (> 500 rpm which provided the powder as a pseudo-liquid state, PLS) led to the redistribution (migration) of the PVP molecules between silica particles previously covered by PVP and free of PVP. This time-dependent rearrangement of the adsorbed PVP molecules caused the formation of a denser polymer layer at the silica surface. The aggregate size of the primary silica particles with adsorbed PVP molecules decreased after treatment. The volume of macropores with a pore radius R p > 25 nm increased due to the decrease in the distances between aggregates in agglomerates because of the adhesive effect of the PVP molecules. However, the volume of micropores at R p < 1 nm decreased because of the penetration of the PVP molecules into the primary silica particle aggregates and the filling of gaps between adjacent particles. A decrease occurred in the amount of adsorbed water in the PVP layer exhibiting a maximum density.

Immobilization of Candida antarctica Lipase B on fumed silica

“…Fumed silica possesses a large specific surface area and exhibits exceptional adsorptive affinity for various organic molecules in aqueous solution including proteins and polymers [26][27][28][29][30][31] . The adsorption of proteins onto fumed silica has been reported to be essentially irreversible 29,32 .…”

Hydrophilic nanocomposites based on polyurethane/poly(2‐hydroxyethyl methacrylate) semi‐IPNs and modified/unmodified nanosilica for biomedical applications

“…The dispersion of nanoparticles may be improved by additional functionalization of their surface to create covalent bonding with polymer matrix. 8,9 Considerable attention has been paid last years also to nanocomposites containing silica nanoparticles. Such nanocomposites were mainly prepared by sol-gel method, where silica clusters were connected to the polymer matrix by chemical (covalent) or physical (mostly hydrogen) bonds.…”

“…[14][15][16][17][18]24 Using 3-D fumed silica nanoparticles core-shell nanocomposites were also prepared and characterized. [25][26][27][28] In our previous works [29][30][31][32][33][34][35][36][37][38][39] dynamic-mechanical behavior, segmental motions, elastic, and physico-mechanical properties have been studied in several polyurethane-poly(2hydroxyethyl methacrylate) semi-interpenetrating polymer networks (PU-PHEMA semi-IPNs) over the temperature range 2140 to 180 C, using combined Atomic force microscopy (AFM), dynamic mechanical analysis (DMA), laserinterferometric creep rate spectroscopy (CRS), and differential scanning calorimetry (DSC) analysis. These systems have basically two-phase, nanoheterogeneous structure with incomplete phase separation, and the pronounced dynamic heterogeneity within the extraordinarily broadened PHEMA and PU glass transitions were observed in these semi-IPNs.…”

Integral equation for calculation of distribution function of activation energy of shear viscosity

“…they can be multimodal. Notice that in the case of mixing of A-300 with A-300/PVP, the migration of polymer molecules between PVP-covered and uncovered silica particles was observed even at low amounts of solvents (30 wt% of water or ethanol) [21]. The migration of the polymer molecules occurs between aggregates (clusters, cages).…”

“…In the case of wetted and dried PVP/A-300 powders, the minimal size of aggregates is 100-200 nm. Thus, there are several types of the cages (clusters) related to (i) small PVP/A-300 aggregates of 20-30 nm in size which includes several particles and several polymer molecules; (ii) larger aggregates of 100-500 nm; (iii) agglomerates of aggregates (>1 µm); and (iv) large continuous coagulation structures in very concentrated suspensions [21][22][23]. One can assume that activated jumps between so different cages (characterized by different numbers of bonds between a polymer molecule and solid particles) correspond to different activation energy.…”