Morphology of Photopolymerized End-Linked Poly(ethylene glycol) Hydrogels by Small-Angle X-ray Scattering

Abstract

Due to the biocompatibility of poly(ethylene glycol) (PEG), PEG-based hydrogels have attracted considerable interest for use as biomaterials in tissue engineering applications. In this work, we show that PEG-based hydrogels prepared by photopolymerization of PEG macromonomers functionalized with either acrylate or acrylamide end-groups generate networks with crosslink junctions of high functionality. Although the crosslink functionality is not well controlled, the resultant networks are sufficiently well ordered to generate a distinct correlation peak in the small angle x-ray scattering (SAXS) related to the distance between crosslink junctions within the PEG network. The crosslink spacing is a useful probe of the PEG chain conformation within the hydrogel and ranges from approximately 6 to 16 nm, dependent upon both the volume fraction of polymer and the molecular weight of the PEG macromonomers. The presence of a peak in the scattering of photopolymerized PEG networks is also correlated with an enhanced compressive modulus in comparison to PEG networks reported in the literature with much lower crosslink functionality that exhibit no scattering peak. This comparison demonstrates that the method used to link together PEG macromonomers has a critical impact on both the nanoscale structure and the macroscopic properties of the resultant hydrogel network.

Impact of secondary reactive species on the apparent decoupling of poly(ethylene glycol) diacrylate hydrogel average mesh size and modulus

“…Recent small-angle X-ray scattering data of PEGDA hydrogels cured by free radical polymerization have revealed that these hydrogels form as nanostructures composed of PEG macromer chains spaced between high functionality crosslinked domains, as shown schematically in Figure 9A. 46 In light of the present data, we hypothesize that the SRS (i.e. NVP, PEGTA) participate in the crosslink junctions in the dense PEGDA regions and perhaps contribute to increased PEGDA densification in these nanostructures (Figure 9B).…”

Designing hydrogels for controlled drug delivery

“…To directly characterize the mesh size, there exist techniques such as confocal microscopy 233 , electron microscopy 72 , atomic force microscopy 234 , small-angle X-ray scattering (SAXS) 235 , and small-angle neutron scattering (SANS) 236 . Electron microscopy enables extremely high spatial resolution, but specimen preparation may alter the morphology of hydrogels.…”

Structurally diverse and readily tunable photocrosslinked chondroitin sulfate based copolymers

“…It has been shown previously that pure PEGDA structure consists of densely crosslinked regions of kinetic chains in a network of loosely entangled poly(ethylene glycol) chains. 45 Multiple methacrylate groups on CS can improve the crosslink density of inherently heterogeneous PEG structure by acting as a multifunctional crosslinker connecting the network domains together. The increased moduli and reduced swelling in PEGDA dominated gels in each group was an indication of more efficient crosslinking (Fig.…”