Nanostructure of PMMA/MAM Blends Prepared by Out-of-Equilibrium (Extrusion) and Near-Equilibrium (Casting) Self-Assembly and Their Nanocellular or Microcellular Structure Obtained from CO2 Foaming.

Suset Barroso-Solares,Victoria Bernardo,Daniel Cuadra-Rodriguez,Javier Pinto

doi:10.3390/nano11112834

Abstract

Blends of poly(methyl methacrylate) (PMMA) and a triblock copolymer poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate) (MAM) have been obtained following both out-of-equilibrium (extrusion) and near-equilibrium (solvent casting) production routes. The self-assembly capability and the achievable nanostructures of these blends are analyzed by transmission electron microscopy (TEM) regarding their production route and potential for the achievement of nanocellular foams by CO2 gas dissolution foaming. The influence of the initial nanostructure of the solids on the obtained cellular structure of bulk and film samples is determined by high-resolution scanning electron microscopy (HRSEM) for diverse foaming conditions (saturation pressure, saturation temperature, and post-foaming stage), taking into account the required use of a foaming mold to achieve foams from films. Moreover, the influence of the nanostructuration on the presence of solid outer layers, typical of the selected foaming process, is addressed. Finally, consideration of a qualitative model and the obtained results in terms of nanostructuration, cellular structure, and foaming behavior, allow proposing a detailed cell nucleation, growth, and stabilization scheme for these materials, providing the first direct evidence of the cell nucleation happening inside the poly(butyl acrylate) phase in the PMMA/MAM blends.

Highlights

Enhancing energetic efficiency is a global technological priority in our society, being promoted by international organizations such as the European Union (EU) and the UnitedNations (UN) [1,2]
The out-of-equilibrium nanostructuration of 90/10 and 25/75 poly(methyl methacrylate) (PMMA)/MAM bulk blends obtained by extrusion (Figure 1) has been reported in previous works [28,29]
The self-assembled nanostructuration of 90/10 PMMA/MAM blends has been found to be highly dependent on the fabrication conditions

Summary

Introduction

Enhancing energetic efficiency is a global technological priority in our society, being promoted by international organizations such as the European Union (EU) and the UnitedNations (UN) [1,2]. Decreasing CO2 emissions, which are directly related to energy consumption, is a key pillar for both organizations aiming to avoid, or lessen, present and future consequences of the global warming [1,2,3]. Among other advances, decreasing the weight of diverse components employed in transportation would directly reduce the energy consumption of this sector (30.8% of the total energy consumption of the EU) [3,4]. Developing high-efficient thermal insulators would lower the energy consumption in household climatization (over half of the 27.2% of the total energy consumption of the EU) [3,5,6]. Some nanomaterials [7], such as nanocellular polymer foams have shown high potential to address both objectives [8,9,10]. The presence of a nanocellular structure inside the polymer provides significant weight reduction, while the

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