Fabrication and Structural Characterization of Module-Assembled Amphiphilic Conetwork Gels

Abstract

Structural analysis of inhomogeneity-free poly(ethylene glycol)− poly(dimethylsiloxane) (PEG−PDMS) amphiphilic conetwork gels has been performed by the complementary use of small-angle X-ray and neutron scattering. Because of the hydrophobicity of PDMS units, the PEG−PDMS gels exhibit a microphase-separated structure in water. Depending on the volume fraction of PDMS, the microphase-separated structure varies from core−shell to lamellar. The obtained X-ray and neutron scattering profiles are reproduced well using a core− shell model together with a Percus−Yevick structure factor when the volume fraction of PDMS is small. The domain size is much larger than the size of individual PEG and PDMS unit, and this is explained using the theory of block copolymers. Reflecting the homogeneous dispersion conditions in the as-prepared state, scattering peaks are observed even at a very low PDMS volume fraction (0.2%). When the volume fraction of PDMS is large, the microphase-separated structure is lamellar and is demonstrated to be kinetically controlled by nonequilibrium and topological effects.

Amphiphilic Polymer Conetworks Based on Interconnected Hydrophobic Star Block Copolymers: Synthesis and Characterization

“…In four of the APCNs, the molar ratio of the hydrophobic MMA to the hydrophilic DMAEMA units in the arms of the stars was fixed at 3–1, with the overall (nominal) degrees of polymerization (DP) of the arms being 10, 20, 30 and 40. This particular composition is expected to result in materials less swollen in water, leading to better‐ordered aqueous nanophases . The remaining two APCNs comprised star block copolymers whose arms were less hydrophobic, with MMA to DMAEMA molar ratios of 1–1, and 1–3, and constant overall (nominal) arm DP equal to 20.…”

“…The more compact nature and the usually large molecular weight of star polymers are expected to introduce fewer network defects related to chain entanglements, and, therefore, allow for more regular organization of the nanophases in the phase separated state. Although most of the APCNs already prepared from amphiphilic star block copolymers presented nanophase separation with only short‐range order, some recent reports revealed morphologies with longer‐range order . In these latter reports, a rather low amount of cross‐linker was used, so as to allow more freedom to the polymer segments to reach a lowest‐energy configuration, resulting in the formation of better‐ordered morphologies within the APCNs.…”

Synthesis and Structural NMR Characterization of Novel PPG/PCL Conetworks Based upon Heterocomplementary Coupling Reactions

“…This is usually fulfilled for networks with two hydrophobic components as presented here. In case of amphiphilic conetworks, potential solubility and phase‐separation issues must be considered, but previous work has shown that this is not necessarily a problem . Finding a common solvent is likely easier than overcoming the problem of a stronger incompatibility in the melt.…”

“…As an important example, Sakai et al introduced a new type of model network designated as tetra‐PEG gel, which is obtained by heterocomplementary coupling of two orthogonally functionalized tetrahedron‐like polyethylene glycol (PEG) macromonomers (A 4 + B 4 ). The approach was later extended to hybrid gels . Such gels are characterized by their homogeneous structure and resultant high mechanical strength.…”

Exploration of Ideal Polymer Networks

“…By playing with the degree of cross‐linking, p , controlled‐defect networks are prepared with which percolation problems can be revisited . Furthermore, by introducing hetero‐co‐prepolymers, various types of novel gels (networks) have been developed, such as non‐swellable implantable gels, very tough “fuse”‐link gels, and amphiphilic conetworks . Furthermore, model polyelectrolyte gels, in which the concentration and spatial distribution of charges are precisely controlled, are now available .…”