Dispersion at Single Unit TiO₂ Nanoparticles Reduced T_g, Induced Chain Disentanglement and Reduced Tensile Modulus in Waterborne Acrylic Coatings

Abstract

Spatially distributed TiO2 nanoparticles induced an order of magnitude decrease of glass transition temperature, Tg, and chain disentanglement in waterborne acrylic coatings. Acrylic/TiO2 coatings are synthesized in situ by batch emulsion polymerization. The copolymer is based on butyl acrylate (BA), methyl methacrylate (MMA), and acrylic acid (AA) with composition 56:42:2 mol%, and nano‐TiO2 (ca. 12 nm) is incorporated up to 3 wt% content. Transmission electron microscopy (TEM) showed that TiO2 is dispersed at nearly single unit throughout the acrylic matrix. The nanoparticle reduced Tg and broadened the temperature range of the glass transition, δTg. The considerable increase of δTg suggests gradients of dynamics. Shear rheometry demonstrated that TiO2 induced chain disentanglement, the rubbery modulus Ge decreased two orders of magnitude with only 1 wt% TiO2 content thus increasing the packing length p (and the reptation tube diameter as dt = kp, k > 1). Consequently, the tensile Young's modulus E decreased an order of magnitude, relative to the neat copolymer. The reduction of Tg, the slowdown of macromolecular dynamics, the chain disentanglement and the increase of dt suggests dynamics modification due to intercalation of the entangled web by the TiO2 nanoparticles, and these results may be ascribed to a nanoconfinement effect.

Crystallization of Polymers with a Reduced Density of Entanglements

“…The idea is to obtain an extensive shear field, which leads to the modification of the material being processed continuously [59][60][61]. It was also announced that the addition of nanoparticles can support polymer disentangling [62][63][64][65][66].…”

Experimental and Theoretical Research on One-Step Oxidative Esterification of Methyl Acrolein with Methanol

“…Methyl methacrylate (MMA), an important organic chemical raw material and polymer monomer, is widely used to produce plexiglass poly­(methyl methacrylate), as well as other resins, plastics, coatings, adhesives, lubricants, and pharmaceutical polymer materials. − The synthetic methods of MMA, derived from fossil feedstock with different carbon atoms, can be divided into three processes: ethylene (C 2 ), acetone (C 3 ), and isobutene/ tert -butanol (C 4 ). In addition, there is a new attempt to synthesize MMA using biomass-derived itaconic acid. − However, the highly toxic hydrogen cyanide and sulfuric acid are employed in the traditional C 3 acetone cyanohydrin process, accounting for more than 60% of capacity, which could require higher safety protection, corrosion prevention, and fund devotion.…”

Acrylic‐styrene/montmorillonite nanocomposites. Melt viscoelasticity and chain dynamics in nanoconfinement

“…The spatial confinement in polymer chains may arise from: (i) macromolecules spatially confined between layered silicates, 7‐10 (ii) macromolecules constrained within nanopores or nanocylinders, 11‐14 or (iii) polymer fractions located between closely packed nanoparticles 15‐20 …”

“…Evidence is growing that nanoconfinement influences the long‐range cooperative motion found at the glass transition. It has been reported that nanoconfinement increased or decreased the glass transition temperature, T g , in small‐molecule materials, 21 and in amorphous polymers 5,17,20,22,23 . Confinement also influenced the rheological properties of ultrathin films of polydimethyl siloxane (PDMS), 24 and of nanoclay/polymer nanocomposites 7‐10 …”