A new approach for the synthesis of model amphiphilic polymer co-networks (ACNs) based on a heterocomplementary coupling reaction of a 2-(4-nitrophenyl)-benzoxazinone terminated tetra-arm polycaprolactone star (tetra-PCL) with an amino-terminated tetra-arm polyethylene glycol star (tetra-PEG) is presented. The reaction conditions (solvent, concentration, and temperature) were varied widely. Reaction kinetics and gelation were analyzed with high-resolution NMR spectroscopy and computer simulations. The results agree with a nearly homogeneous mixture where local composition fluctuations affect kinetics only after most of the molecules are attached to the gel. Viscometry, dynamic light scattering data, and literature data for the solubility parameters were combined to provide estimates for the Flory−Huggins interaction parameter of the two star polymers in toluene, chloroform, and THF as solvents. These estimates allow one to collapse equilibrium swelling data in different solvents on a universal curve. Multiple quantum NMR analysis shows an enhanced formation of double connections between the same pair of stars as compared to preceding work on tetra-PEG gels made by the same cross-linking strategy but with a different coupling reaction. Besides this last observation, the remaining results indicate that the networks possess a near model-like structure with only a small fraction of pending arms as the most relevant type of network defects.

We investigate the swelling of polymer model networks prepared at different polymer volume fractions and in solvents of different quality. We extend the existing theory to describe residual bond orientations (the vector and the tensor order parameters) for theta, good, and athermal solvents and put these relations in context with modulus at preparation conditions and the equilibrium degree of swelling. We find good agreement with the assumption of affine swelling for the weakly entangled networks of our study. The same scaling relations (up to numerical coefficients) are obtained for the vector order parameter, m, and the tensor order parameter, S, as a function of the preparation conditions, network structure, the equilibrium degree of swelling, Q, and the modulus at swelling equilibrium, G. We obtain m ∝ Q –2 and G ∝ m 3/2 for swelling in theta solvents and m ∝ Q –1.08 with G ∝ m 2.14 in the good-solvent regime, in both cases independent of preparation conditions. Modulus and residual bond orientation are related by G ∝ ϕ0 m and G ∝ ϕ0 1.23 m as a function of the preparation polymer volume fraction ϕ0 for theta solvents and good solvents, respectively. Computer simulations and experimental data for the good-solvent regime show good agreement with the predictions.

A new approach for the synthesis of model amphiphilic polymer co-networks (ACN) based on a hetero-complementary reaction of an oxazinone terminated tetra-arm polycaprolactone star (tetra-PCL) with an amino-terminated tetra-arm polyethylene glycol star (tetra-PEG) is presented. The reaction conditions (solvent, concentration, temperature) were varied widely. Reaction kinetics and gelation were analyzed with high resolution NMR spectroscopy and computer simulations. The results agree with a nearly homogeneous mixture where local composition fluctuations affect kinetics only after most of the molecules are attached to the gel. Viscometry, dynamic light scattering data and literature data for the solubility parameters were combined to provide estimates for the Flory-Huggins interaction parameter of the two star polymers in toluene, chloroform, and THF as solvents. These estimates allow to collapse equilibrium swelling data in different solvents on a universal curve. Multiple quantum NMR analysis shows an enhanced formation of double connections between the same pair of stars as compared to preceding work on tetra-PEG gels made by the same cross-linking strategy but with a different coupling reaction. Besides of this last observation, the remaining results indicate that the networks possess a near model like structure with only a small fraction of pending arms as most relevant type of network defects.