Viscosifying a Noncovalently Joined Polymer Nanoparticle Solution upon Heating

Abstract

We report the synthesis of a series of statistical terpolymer poly­[(methyl methacrylate)-co-lauryl methacrylate-co-2-((3,5-bis­(4-carbamoyl-3-(trifluoromethyl)­phenoxy)­benzyloxy)­carbonylamino)­ethyl methacrylate] (P­(MMA-co-LMA-co-BMA)) by reversible addition–fragmentation chain transfer polymerization and their aggregation behaviors in solution. In toluene, the solution behavior of terpolymer was controlled by the molar fractions of lauryl methacrylate (LMA) and benzamide-containing methacrylate (BMA) in the polymer, which increased solubility and promoted hydrogen bonding between the primary aromatic amides, respectively. Temperature-dependent 1H NMR spectroscopy also indicated gradual dissociation of the hydrogen bonds with increasing temperature. For the polymer containing 2.7 mol % of LMA and 2.7 mol % of BMA repeating units, we demonstrated that dissolving the polymer in tetrahydrofuran as a good solvent and switching the solvent with toluene produced polymer nanoparticles with diameters of several tens of nanometers, as observed by dynamic light scattering. Intramolecular hydrogen bonding was dominant and induced the noncovalent chain collapse. When the temperature of the particle dispersion in toluene at a concentration > 30 mg/mL was increased from RT to 50 °C, a significant increase in viscosity was observed. This behavior was not observed in a toluene solution of poly­(methyl methacrylate), which showed decreased viscosity at a higher temperature. The viscosity increase was accompanied by a decrease in the particle size, and both were attributed to the dissociation of some intramolecular hydrogen bonds within the particles, which can increase the number of individual chains in toluene and result in more intermolecular interactions.

Preparation of Well-Exfoliated Poly(ethylene-co-vinyl acetate)/α-Zirconium Phosphate Nanocomposites

“…To prepare a well-exfoliated polymer nanocomposite, it is ideal to maintain the nanoplatelets’ exfoliation state throughout the entire preparation process since nanoplatelet exfoliation in a solvent cannot guarantee its full exfoliation upon incorporation of the polymer. By introducing the polymer into the nanoplatelet solution, the entire thermodynamic and kinetic conditions may be greatly altered . Good compatibility between nanoplatelets and the polymer is required for optimal dispersion.…”

“…The DLS correlation function is a useful tool to trace the time-dependent particle size change when diluted in the solvent. Brownian motion of nanoparticles in the solvent can be accurately correlated to the hydrodynamic diameter based on diffusion . The intensity of the scattered light measured with DLS is heavily weighted toward large particles over smaller particles.…”

“…The nanoparticle dispersion and exfoliation states in the PEVAc-containing solution may also be affected by the solvent drying process . To determine the ZrP–solvent interaction on stabilization of ZrP exfoliation in the presence of PEVAc, DLS was performed . First, THF was used to mix the PEVAc and ZrP-AO at a weight ratio of PEVAc/ZrP-AO = 4:1.…”

“…By introducing the polymer into the nanoplatelet solution, the entire thermodynamic and kinetic conditions may be greatly altered. 37 Good compatibility between nanoplatelets and the polymer is required for optimal dispersion. To ensure the full exfoliation and dispersion of ZrP in the PEVAc matrix, it is important to study ZrP behavior throughout the entire process, including the solution mixing and drying processes.…”

“…Brownian motion of nanoparticles in the solvent can be accurately correlated to the hydrodynamic diameter based on diffusion. 37 The intensity of the scattered light measured with DLS is heavily weighted toward large particles over smaller particles. Large particles diffuse slower; thus, the correlation intensity is retained for a longer period of time compared to smaller particles.…”