Structural Characterization of Amphiphilic Conetworks in Selective and Nonselective Solvents Using 1H NMR and SAXS

We investigate the structural properties of model amphiphilic conetworks made by heterocomplementary end-linking of tetra-poly(ethylene glycol) tetra-poly(ϵ-caprolactone) PCL star polymers in selective and nonselective solvents using small-angle X-ray scattering, nuclear magnetic resonance (NMR) diffusometry, and double-quantum magic-angle spinning (DQ MAS) NMR techniques. The X-ray scattering experiments reveal the correlation lengths of our networks, including postcuring effects, and the microphase separation (MPS) of the networks swollen by a selective solvent, with cluster sizes independent of concentration. An estimation of hydrodynamic screening length as the length scale governing the diffusion process is achieved by monitoring the diffusion coefficients of polysaccharides and polystyrenes with different molecular weights. Furthermore, chemical-shift-resolved local chain mobilities in the microphase-separated system are observed using DQ MAS NMR, demonstrating immobilization of the linker end group and melt-like dynamics for clustered PCL chains, both of which are in qualitative agreement with bond-fluctuation Monte Carlo simulations of comparable model structures. Our analyses provide valuable insights into the structural properties and behavior of amphiphilic conetworks and the process of MPS under strong topological constraints, highlighting the effects of postcuring in a polymer network with star-shaped building blocks.