Bound fractions of methacrylate polymers adsorbed on silica using FTIR

Abstract

The H-bonding of carbonyl groups on a series of methacrylate polymers with silanols on fumed silica was studied with transmission FTIR. The set included poly(alkyl methacrylates) with alkyl groups, (n-C n H 2nþ1 ) of n ¼ 1, 2, 4, and 12 and poly(benzyl methacrylate). Shifts in the vibrational frequencies for bound carbonyl groups (of $20 cm À1 lower than those found in the bulk) were observed in the adsorbed polymer samples. A series of samples with different adsorbed amounts (varying from 0.5 to 2.0 mg m À2 ) of each polymer was prepared to determine the effect of the side chain on the H-bonding. The fractions of bound carbonyls, p, for each of the methacrylate polymers studied, were calculated from a model based on the ratios of the absorption coefficients of the bound to free carbonyl resonances,The X values were determined from linear regressions of the ratios of the free to bound carbonyl intensities as a function of the amounts of adsorbed polymer, M t . The bound fractions, p, were observed to decrease with increase in adsorbed amounts and with increase in the lengths of the side chains of the methacrylate polymers, except for poly(lauryl methacrylate) (PLMA). PLMA has a very low glass transition temperature (T g ) and is likely rubbery on the surface, whereas the other polymers are likely glassy at ambient temperature.

Thermal Properties of PMMA on Silica Using Temperature‐Modulated Differential Scanning Calorimetry

“…The smooth curve is based on the model with fixed amount of tightly bound polymerof m ″ B = 1.21 mg/m 2 . Shown for comparison are the composite of results for PMMA of different molecular masses and solvents from FTIR …”

“…The bound fraction decreased smoothly with increased adsorbed amount. For comparison, the data for the bound fractions of the same polymer on silica from FTIR are also shown …”

“…Results from ESR (which are similar to NMR) measurements were, however, higher than (in the range of 1 to 0.5) from IR over a similar range of concentrations, consistent with the notion that the estimation of bound fraction depends on different experimental technique used . NMR and ESR techniques are not only sensitive to the segments that are directly bound, but also the segments that are a few Ångstroms from surface . In contrast, shifts in carbonyl frequencies in IR spectrum are only sensitive to segments that are directly attached to the surface, resulting lower estimates of bound fractions.…”

Low-temperature polymerization of methyl methacrylate emulsion gels through surfactant catalysis

“…The adsorbed polymer undoubtedly competed with cationic surfactant (CTAB) for surface coverage [37,38]. This strong binding also resulted in T g increase of 20°C in PMMA/silica/CTAB composites compared to the bulk polymer and the binary PMMA/CTAB systems [36,39,40]. In fact, since there was little or no thermal activity around the bulk PMMA T g , it may be concluded that most of the PMMA was adsorbed on silica.…”

Equilibria and kinetics of phenol adsorption on a toluene-modified hyper-cross-linked poly(styrene-co-divinylbenzene) resin

“…Macroporous cross-linked poly(styrene-co-divinylbenzene) (PS) or polymethacrylate resins have displayed excellent adsorption behaviors toward aromatic compounds [1][2][3][4], and hence these resins are increasingly applied for the efficient removal and recycling of aromatic compounds [5]. In the 1970s, Davankov developed a hyper-cross-linking technique, and a type of novel hyper-cross-linked PS resin was prepared from linear PS or low cross-linked PS through the use of bifunctional cross-linking agents and Friedel-Crafts catalysts [6,7].…”