Miniemulsion copolymerization of (meth)acrylates in the presence of functionalized multiwalled carbon nanotubes for reinforced coating applications.

Bertha T Pérez-Martínez,Radmila Tomovska,Lorena Farías-Cepeda,José M Asua,Lucero Rosales-Marines,Víctor M Ovando-Medina

doi:10.3762/bjnano.8.134

Bertha T Pérez-Martínez, Radmila Tomovska + Show 4 more

Open Access

https://doi.org/10.3762/bjnano.8.134

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Abstract

Film forming, stable hybrid latexes made of methyl metacrylate (MMA), butyl acrylate (BA) and 2-hydroxyethyl methacrylate (HEMA) copolymer reinforced with modified multiwalled carbon nanotubes (MWCNTs) were synthesized by in situ miniemulsion polymerization. The MWCNTs were pretreated by an air sonication process and stabilized by polyvinylpyrrolidone. The presence of the MWCNTs had no significant effect on the polymerization kinetics, but strongly affected the polymer characteristics (Tg and insoluble polymer fraction). The performance of the in situ composites was compared with that of the neat polymer dispersion as well as with those of the polymer/MWCNT physical blends. The in situ composites showed the presence of an additional phase likely due to the strong interaction between the polymer and MWNCTs (including grafting) that reduced the mobility of the polymer chains. As a result, a substantial increase of both the storage and the loss moduli was achieved. At 60 °C, which is above the main transition region of the polymer, the in situ composites maintained the reinforcement, whereas the blends behaved as a liquid-like material. This suggests the formation of a 3D network, in good agreement with the high content of insoluble polymer in the in situ composites.

Highlights

Carbon nanotubes (CNTs) are hollow, fiber-like materials, with a diameter on the nanometer scale and a relatively long length on the micrometer scale, resulting in a very high aspect ratio material
Film-forming polymer–multiwalled CNTs (MWCNTs) composite dispersions were synthesized in situ by miniemulsion polymerization of methyl metacrylate (MMA)/
The presence of the MWCNTs had no significant effect on polymerization kinetics, but strongly increased the fraction of insoluble polymer that was attributed to the interaction between the OH groups of the copolymer and the PVP-stabilized MWCNTs and as well to the possible grafting of polymer chains onto MWCNTs

Summary

Introduction

Carbon nanotubes (CNTs) are hollow, fiber-like materials, with a diameter on the nanometer scale and a relatively long length on the micrometer scale, resulting in a very high aspect ratio material. Two types of CNTs exist, those made of a single graphene layer rolled-up into a cylinder (single-walled carbon nanotubes (SWCNTs)) or multiwalled CNTs (MWCNTs) that consist of two or more sheets of graphene concentrically rolled around a hollow core. Due to the excellent electrical, optical, thermal, mechanical, and chemical properties of CNTs, they are considered to be an advanced material that may be useful for multiple applications, one of which is polymer composite synthesis [1,2,3,4]. By inclusion of CNTs in polymer matrices, nanostructured materials with improved mechanical, electrical and thermal properties may be synthesized. One way to improve this interaction is to functionalize the surface of CNTs, either by covalent attachment or through the supramolecular adsorption or wrapping of suitable functionalities and even surface active substances [1,2,4,5]

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