Segmental Dynamics of Interfacial Poly(methyl acrylate)-d₃ in Composites by Deuterium NMR Spectroscopy

Abstract

The interface in composite materials containing an ultrathin layer of poly(methyl acrylate)-d(3) (PMA-d(3)) on silica was studied using deuterium NMR. PMA-d(3) was deposited from solution at saturation coverage from toluene onto silica. The samples were dried and composite samples made by hot pressing the PMA-d(3)/silica samples with hydrogenated polystyrene (PS) and high (HMW) and low (LMW) molecular weight hydrogenated poly(methyl acrylate) (PMA) as the overlayer. The interfacial layers of PMA-d(3) were studied at the air-polymer-silica and polymer-polymer-silica interfaces using deuterium solid-state quadrupole-echo NMR and the results compared to those for the bulk polymer. It was found that for samples at the air-polymer-silica interface, some of the polymer segments in the surface sample had segmental mobility higher than that of the corresponding bulk PMA-d(3) sample at the same temperature. When overcoated with unlabeled polymer, the interfacial polymer at the polymer-polymer-silica interface showed reduced mobility due to the presence of the overlayer. The adsorbed PMA-d(3), in the composite samples, decreased in mobility in the order of LMW-PMA > HMW-PMA > PS. The PS sample caused the greatest reduction in the PMA-d(3) interfacial mobility. The order was consistent with the segmental mobilities of the polymers used for the overlayers. The lower the mobility of the polymer used for the overlayer, the more restricted were the polymer segments in the adsorbed PMA-d(3) layer.

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

“…This notion was verified by studies done on a system where unlabeled polymer was placed on the top of labeled polymer, causing the regions of high mobility to disappear. [41] One might expect that such behavior should be observed in the TMDSC measurements as well. Clearly, an increased T g of as much as 35-45°C was easily observed here and the amount of the tightly-bound polymer seemed to level off after m 00 B ¼ 1.21 mg/m 2 , consistent with NMR studies on similar systems.…”

“…The segments near the polymer‐air interface were more mobile (lower T g ) than those in the bulk polymer while the segments that were close to the silica surface were less mobile (higher T g ). This notion was verified by studies done on a system where unlabeled polymer was placed on the top of labeled polymer, causing the regions of high mobility to disappear . One might expect that such behavior should be observed in the TMDSC measurements as well.…”

Molecular mass and dynamics of poly(methyl acrylate) in the glass-transition region

“…[12][13][14][15][16][17][18][19][20][21][25][26][27][28] Deuterium NMR line shapes provide information about segmental dynamics through the glasstransition region due to the coupling of the C-D bond vectors with the cooperative motions of the polymer chains. The 2 H NMR spectra for unoriented solidlike polymers consist of powder patterns from randomly oriented C-D bonds.…”

Melting and crystallization behavior of metallic alloy in the composites with polyacrylate

“…The physical properties of polymer at surface or interface have attracted both scientific and industrial interests. [1][2][3][4][5][6][7] Whereas the physical properties of nonpolar polymers at the surface phase can differ from those of the polymers at bulk phase, 8 the interfacial interaction between polar polymer and metal dominates the physical properties of the polymer because of their strong interaction. 9 The strong interaction between polar polymer and metal arranges the polar groups, and changes the mobility of the main chains of the polymer.…”