SANS study of highly resilient poly(ethylene glycol) hydrogels

Abstract

Polymer networks are critically important for numerous applications including soft biomaterials, adhesives, coatings, elastomers, and gel-based materials for energy storage. One long-standing challenge these materials present lies in understanding the role of network defects, such as dangling ends and loops, developed during cross-linking. These defects can negatively impact the physical, mechanical, and transport properties of the gel. Here we report chemically cross-linked poly(ethylene glycol) (PEG) gels formed through a unique cross-linking scheme designed to minimize defects in the network. The highly resilient mechanical properties of these systems (discussed in a previous publication1), suggests that this cross-linking technique yields more homogeneous network structures. Four series of gels were formed based on chains of 35,000 g/mol, (35K), 12,000 g/mol (12K) g/mol, 8,000 g/mol (8K) and 4,000 g/mol (4K) PEG. Gels were synthesized at five initial polymer concentrations ranging from 0.077 g/mL to 0.50 g/mL. Small-angle neutron scattering (SANS) was utilized to investigate the network structures of gels in both D2O and d-DMF. SANS results show the resulting network structure is dependent on PEG length, transitioning from a more homogeneous network structure at high molecular weight PEG to a two phase structure at the lowest molecular weight PEG. Further investigation of the transport properties inherent to these systems, such as diffusion, will aid to further confirm the network structures.

Testing Classical Approach to Polymer Solutions on SAXS Data of λ-Carrageenan, κ-Carrageenan and Methylcellulose Systems

“…This approach was namely originally developed and then also successfully applied mainly to the SANS data. [7][8][9][10][11][12][13][14][15] Even though there are some similar studies available also on the SAXS data nowadays, we still miss thorough systematic reports on such analysis of experimental SAXS data. The lack of such studies could be reasoned by the necessity of some additional considerations that must be dealt with the SAXS data, i.e.…”

“…For the evaluation and interpretation of the SAXS data we followed and adequately modified the so-called "classical approach" developed for the interpretation of similar SANS data on polymer solutions and gels. This approach was already extensively used and tested in the case of SANS on polymer solutions and simple gels [8][9][10][11][12][13][14][15] and recently already also on some SAXS data. [16][17][18][19] In the case of SAXS data one needs to account for the experimental broadening effects and correspondingly slightly modify the fitting scattering function.…”

Small angle neutron scattering contrast variation reveals heterogeneities of interactions in protein gels

“…Note that Eq. 1 has also been previously used to account for the scattering of methylcellulose solutions 32 , POE solutions 31 , PEG hydrogels 33 , and peptide hydrogels 34 .…”

Emerging Corrosion Inhibitors for Interfacial Coating

“…However, a steep upturn was observed in SANS curves, indicating the presence of PEG chain clusters or defects where these inhomogeneities disappear in swelled sample. Furthermore, Bhatia and co-workers designed a unique form of chemically cross-linked PEG gels to minimize defects in the network [134]. SANS was utilized to investigate the network structures of gels in two different solvents: D 2 O and d-DMF.…”