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Ionic-covalent entanglement hydrogels were fabricated by 3D-printing.

An aqueous reversible-deactivation radical polymerization (RDRP) approach is used to synthesize sodium polystyrene sulfonate directly from functionalized monomers to give uniformly and completely sulfonated materials. Reproducible gram scale syntheses are achieved under simple one pot reaction conditions at ambient temperatures, and full monomer conversions are achieved within approximately 3 h. Reaction variables such as pH, sodium chloride concentration, and methanol cosolvent have a significant effect on the molecular weights (M n ≈ 20,000-400,000 gÁmol −1 ) obtained by gel permeation chromatography coupled multiangle light scattering. Observed dispersities were reasonably narrow: Ð ≈ 1.05-1.3. A parametric optimization, rather than direct variation of the monomer to initiator ratio, resulted in some of the highest molecular weight polymers by an RDRP approach. Linear progression between M n and monomer conversion occurs at a neutral reaction pH, which results in narrow polymer molecular weight distributions, along with high end-group fidelity as demonstrated with chain extension reactions.

Selected solution and bulk properties were measured for perfectly para-sulfonated sodium poly­(styrene sulfonate) (NaP4SS) and commercially obtained poly­(styrene sulfonate) (NaPSS). NaP4SS was made by the controlled radical polymerization of 4-styrene sulfonate monomer, whereas the commercially obtained NaPSS (C-NaPSS) was made from the post-treatment of polystyrene. A discrepancy in the degree of sulfonation was determined by 1H NMR, 13C NMR, and Fourier transform infrared spectroscopy (FT-IR), which showed that C-NaPSS samples had degrees of sulfonation of 89–95%. Conformation plots obtained by size exclusion chromatography coupled with multiangle light scattering (SEC–MALS) produced Flory exponent (v) values of 0.475 ± 0.015 for C-NaPSS compared to 0.57 ± 0.02 for NaP4SS, across a range of measured molecular weights. The partial specific volume of NaP4SS was measured to be slightly lower than that of C-NaPSS. Furthermore, C-NaPSS exhibited a glass transition temperature (T g) of approximately 228 °C with slight variation depending on molecular weight, but no observable T g was found for NaP4SS over a broad temperature range of −50 to 420 °C. Both polymers showed thermal onsets of degradation in the 420–440 °C range.

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