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Title: Polyacrylamide hydrogels. V. Some strands in a polymer network bear loads, but all strands contribute to swelling
When a poly mer net workis stretched, so me poly mer strands do not bearloads. Exa mplesinclude looped strands, dangling strands, and extre mely long strands. When the poly mer net work is sub mergedin asolvent, ho wever, allstrands mix withsolvent molecules. This distinction bet ween strandsthat bearloads andstrandsthat do notleads usto modifythe Flory-Rehner model. The modified modelhasthreeparameters:thedensityofload-bearingstrands, N,thedensityofall strands,M , andtheinteraction para meter,χ. For a poly mer net worksub mergedin areservoir of solvent and bearingtriaxialstresses,the modified model provides equations ofstate,relatingthe stressestostretches, as well asthe che mical potential ofsolvent molecules andte mperatureinthe reservoir. We synthesize polyacryla mide hydrogels using precursors of various concentrations of mono mer, crosslinker, and transfer agent. We deter mine the three para meters N, M , and χ by fittingthe modified modeltoseveral experi ments,includingfrees welling,fasttension, andstress relaxation. In all sa mples tested, M is several ti mes N , whereas χ is nearly constant. This work de monstrates the consequences of the notion that so me poly mer strands in a poly mer net work b e ar l o a ds, b ut all str a n ds c o ntri b ut e t o s w elli n g.  more » « less
Award ID(s):
2011754
PAR ID:
10501569
Author(s) / Creator(s):
; ;
Publisher / Repository:
Elsevier
Date Published:
Journal Name:
Journal of the Mechanics and Physics of Solids
Volume:
168
Issue:
C
ISSN:
0022-5096
Page Range / eLocation ID:
105017
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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