Design of Nanocomposites by Vapor-Phase Assisted Surface Polymerization

Abstract

Exfoliated polymer/clay nanocomposites with high clay contents were facilely constructed by the vapor-phase assisted surface polymerization of methyl methacrylate (MMA) with montmorillonite premodified with a trimethylstearyl ammonium salt and a free radical initiator: 2,2′-azobis(isobutyronitrile). This method required only premodified MMT and vaporized vinyl monomer without any prehomogenizing and postpolymerization processes. The exfoliated structure of the nanocomposites, which was confirmed by X-ray diffraction analysis, was retained even after melt processing.

Melt-Processable Nanocomposites Grafting-From Platelet Surfaces by Vapor-Assisted Surface Polymerization

“…However, the layered structure of C18MMT was not recovered until the original value (d-spacing 2.30 nm) was reached. As reported previously [29], a few polymer chains may be covalently bound on the silicate surfaces and the weak anchoring effect of these grafted chains may explain incomplete recoveries of d-spacing values after the melt processing. Figure 3 shows changes in XRD profiles of blended C18/ C6MMT-based composite samples: (a) composite-sample 2/PMMA (sample 6) and (b) composite-sample 4/PSt (sample 8), in comparison with the original composite samples (samples 2 and 4).…”

“…Preparation pathways are shown in Scheme 1. Previously, it was confirmed that an acetone solution of AIBN smoothly diffused into C18-modified silicate interlayers, and that the initiator remained in the interlayers after drying the silicates [29]. Insertion of AIBN into the silicate interlayers successfully proceeded, with the expected increase in interlayer d-spacing.…”

“…Typical procedure: initiator AIBN intercalated C18/C6MMT (A-C18/C6MMT) was prepared in a similar manner as reported elsewhere in detail [29]. Before VASP, to intercalate the initiator AIBN into the silicate layers, C18/ C6MMT (2.41 g) was treated with a 1 mM acetone solution (500 mL) of AIBN at a 1 : 30 weight ratio to C18/C6MMT at 25…”

“…Polymer chains then grow on the surfaces by filling the spaces. Recently, a simple method for construction of vinyl polymer/clay nanocomposites by VASP of methyl methacrylate (MMA) was reported, by which a completely exfoliated poly(methyl methacrylate) (PMMA)/MMT nanocomposite was obtained [29]. It was also revealed that, because of a particular interaction between silicate platelet surfaces and MMA units in copolymer chains, a small number of MMA units in a styrene-MMA copolymer induced the exfoliation of layered silicates [30].…”

Simple Procedure for Polystyrene-Based Nanocomposite Preparation by Vapor-Phase-Assisted Surface Polymerization

“…The number-and weight-average molecular weights, analyzed by SEC, of the isolated polymer were 1.1 Â 10 6 and 2.7 Â 10 6 , respectively, values that are high enough for PMMA to exfoliate the silicate layers. 14 The VASP product in entry 1 was compared with a product of a solution polymerization of St (entry Sol-1), which was carried out in a toluene suspension of the same AIBN pretreated C18MMT powder. In spite of a comparable amount of product (120 mg), the XRD profile of the product showed only a small expansion in the d-spacing (3.4 nm) between the silicate layers ( Figure 1).…”