Jump to main content
Jump to site search

Issue 35, 2018
Previous Article Next Article

Impact of stereochemistry on rheology and nanostructure of PLA–PEO–PLA triblocks: stiff gels at intermediate L/D-lactide ratios

Author affiliations

Abstract

We report rheology and structural studies of poly(lactide)–poly(ethylene oxide)–poly(lactide) (PLA–PEO–PLA) triblock copolymer gels with various ratios of L-lactide and D-lactide in the PLA blocks. These materials form associative micellar gels in water, and previous work has shown that stereoregular triblocks with a L/D ratio of 100/0 form much stiffer gels than triblocks with a 50/50 L/D ratio. Our systems display an unexpected maximum in the storage modulus, G′, of the hydrogels at intermediate L/D ratio. The impact of stereochemistry on the rheology is very striking; gels with an L/D ratio of 85/15 have storage moduli that are ∼1–2 orders of magnitude higher than hydrogels with L/D ratios of 100/0. No stereocomplexation is observed in the gels, although PLLA crystals are found for gels with L/D ratios of 95/5 and 90/10, and SANS results show a decrease in the intermicellar spacing for intermediate L/D ratios. We expect the dominant contribution to the elasticity of the gels to be intermicellar bridging chains and attribute the rheology to a competition between an increase in the time for PLA endblocks to pull out of micelles as the L/D ratio is increased and PLLA crystallization occurs, and a decrease in the number of bridging chains for micelles with crystalline PLA domains, as formation of bridges may be hindered by crowded crystalline PLA domains. These results provide a new strategy for controlling the rheology of PLA-based hydrogels for potential applications in biomaterials, as well as fundamental insights into how intermicellar interactions can be tuned via stereochemistry.

Graphical abstract: Impact of stereochemistry on rheology and nanostructure of PLA–PEO–PLA triblocks: stiff gels at intermediate l/d-lactide ratios

Back to tab navigation

Supplementary files

Publication details

The article was received on 31 Jul 2018, accepted on 13 Aug 2018 and first published on 13 Aug 2018


Article type: Paper
DOI: 10.1039/C8SM01559G
Citation: Soft Matter, 2018,14, 7255-7263
  •   Request permissions

    Impact of stereochemistry on rheology and nanostructure of PLA–PEO–PLA triblocks: stiff gels at intermediate L/D-lactide ratios

    X. Yin, D. R. O. Hewitt, S. P. Quah, B. Zheng, G. S. Mattei, P. G. Khalifah, R. B. Grubbs and S. R. Bhatia, Soft Matter, 2018, 14, 7255
    DOI: 10.1039/C8SM01559G

Search articles by author

Spotlight

Advertisements