Effect of Poly(ethylene glycol) Grafting Density on Methylcellulose Fibril Formation

Journal Article · Thu Nov 15 00:00:00 EST 2018 · Macromolecules

DOI:https://doi.org/10.1021/acs.macromol.8b01899· OSTI ID:1492985

Morozova, Svetlana ^[1]; Schmidt, Peter W.  ^[1]; Bates, Frank S.  ^[1]; Lodge, Timothy P.  ^[1]

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1. Univ. of Minnesota, Minneapolis, MN (United States)

Herein we investigate the effect of short-chain poly(ethylene glycol) (PEG) graft density on the formation of methylcellulose (MC) fibrils at elevated temperatures. Thiol–ene click chemistry was used to systematically graft 800 and 2000 g/mol PEG onto the backbone of allylated MC, with a wide range of grafting densities from 0.7% to 33%. As determined from light scattering, grafting leads to an increase in the persistence length of this semiflexible copolymer, by as much as a factor of 10. Upon heating, SAXS and AFM studies show that fibril formation is suppressed at around 10% grafting density for shorter PEG grafts, corresponding to persistence lengths about ~22 nm. For longer grafts fibril formation is suppressed at 7% grafting density, at around the same ~22 nm persistence length. The radius of the fibrils increases with the square root of the persistence length of the chains, which is consistent with a theory for the radius of twisted chains. The ability to form networks at 80 °C is highly correlated to the ability to form fibrils, and accordingly the modulus systematically decreases with grafting density. When the fibril formation is suppressed, MC solutions no longer form solid networks. Therefore, grafting modulates the molecular architecture and gelation properties of MC and also provides new insight into the structure of MC fibrils.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: National Science Foundation (NSF); Northwestern University; E.I. DuPont de Nemours & Co.; The Dow Chemical Company; USDOE Office of Science (SC)
• Grant/Contract Number: DMR-1420013; AC02-06CH11357
• OSTI ID: 1492985
• Journal Information: Macromolecules, Vol. 51, Issue 23; ISSN 0024-9297
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Nanofibers
Alcohols
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Chemical structure
Polymers