Effect of Alkyl Side Chain Length on Relaxation Behaviors in Poly(n-alkyl Acrylates) and Poly(n-alkyl Methacrylates)

Approaching Polymer Dynamics Combining Artificial Neural Networks and Elastically Collective Nonlinear Langevin Equation

The analysis of structural relaxation dynamics of polymers gives an insight into their mechanical properties, whose characterization is used to qualify a given material for its practical scope. The dynamics are usually expressed in terms of the temperature dependence of the relaxation time, which is only available through time-consuming experimental processes following polymer synthesis. However, it would be advantageous to estimate their dynamics before synthesizing them when designing new materials. In this work, we propose a combined approach of artificial neural networks and the elastically collective nonlinear Langevin equation (ECNLE) to estimate the temperature dependence of the main structural relaxation time of polymers based only on the knowledge of the chemical structure of the corresponding monomer.

Impact of the Pendant Group on the Chain Conformation and Bulk Properties of Norbornene Imide-Based Polymers

Three series of well-defined norbornene imide-based polymers with different pendant groups were synthesized to investigate the effect of the pendant group on the polymer conformation in solution and bulk melt properties. Each of these three series was examined by analyzing the polymers' bulk z-average radius of gyration via static light scattering and the polymers' melt viscoelastic properties via oscillatory measurements and differential scanning calorimetry. Sterically bulky pendant wedge groups modestly increase the rodlike conformation of the norbornene-imide polymer, however, the inherent rigidity of the polymer main-chain can still be observed with less bulky substituents. In stark contrast, the different side groups significantly impacted the bulk viscoelastic and thermal properties. By increasing the pendant group size, the chain diameter of the polymer increases and lowers the entanglement modulus. Finally, as the wedge pendant group size increases, the segmental relaxation time and the fragility index of these norbornene-based polymers are decreased.

Core-shell-shell cytocompatible polymer dot-based particles with near-infrared emission and enhanced dispersion stability

Polymer dots (PDs) are promising fluorescent probes for biomaterials applications. Here, novel cytocompatible composite PD particles have been synthesised with a core-shell-shell morphology. The particles show near-infrared emission, improved fluorescent brightness and enhanced colloidal stability compared to pure PDs. The particles also show non-radiative resonance energy transfer (NRET) with a model dye.

Polyrotaxane Glass: Peculiar Mechanics Attributable to the Isolated Dynamics of Different Components

The molecular dynamics of condensed polymers are directly linked to practically important mechanical properties, such as glass transition behavior and impact strength. We present a unique viscoelastic glass-forming polyrotaxane that is comprised of a main chain polymer and threaded cyclodextrins. The abnormally broad glass transition phase is attributed to the segment motion, which is unprecedentedly insusceptible to cooperative motion with neighboring chains until vitrification is completed. Even in the glass state, in which the cyclic components, occupying >80 wt % of the material, are vitrified, the main chain polymer retains high mobility within the glassy porous framework. The anomalous mobility of the polymer chains causes strong subrelaxation that changed the elastic modulus about 3-fold. These results demonstrate that the unique dynamics and mechanics are attributable to the loose correlation between different components, suggesting the possible creation of unprecedented mechanical properties based on the molecular design of mechanically interlocked polymers.