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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Understanding the reinforcement mechanism by dispersing nanoscale particles into a polymer matrix is a critical challenge toward refining control of the composite properties. In this paper, the morphologies and interactions of cellulose nanocrystal/poly(acrylic acid) (CNC/PAA) nanocomposite hydrogels are demystified based on a facile synthetic platform. Two sources of CNCs with different aspect ratios are applied to model the reinforcement process, and the uniaxial tensile measurements indicate that the CNC aspect ratio and the nanocomposite mechanical behaviors are coupled, where the values of aspect ratios and nonpermanent interactions between the fillers and matrix dominate the reinforcement. Dynamic mechanical analysis is performed to examine the nature of the constrained polymer as the semicrystalline fractions, and the results indicate that polymer chain mobility in the vicinity of CNC surfaces is significantly reduced, providing new insight into the origin of the reinforcement mechanism. Rheological analysis and transmission electron microscopy observations show that both stepwise dissociation and polymer chain rearrangements contribute to the viscoelastic behaviors of the nanocomposite hydrogels. The increased modulus of the hydrogels is correlated to the volume of the constrained polymer, where the CNCs impart significant enhancement to the entanglement network. This study of the structure-property relationship deepens the understanding of the filler reinforcement mechanism and provides valuable knowledge for designing high performance nanocomposite hydrogels from cellulose as a raw material.
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PMID:Revealing strong nanocomposite hydrogels reinforced by cellulose nanocrystals: insight into morphologies and interactions. 2429 12

We present a facile strategy for the fabrication of mechanically tough and self-recoverable nanocomposite hydrogels reinforced by surface-modified cellulose nanocrystals. Polyacrylamide grafted cellulose nanocrystal (CNC-g-PAM) was first synthesized by ceric salt initiated surface graft polymerization of acrylamide onto CNC, then incorporated into chemically crosslinked poly(acrylic acid) (PAA) networks to obtain dual-crosslinked CNC-g-PAM/PAA nanocomposite hydrogels. CNC-g-PAM acted as both interfacial compatible nanofillers and physical crosslinkers through reversible hydrogen bonds between PAA and PAM on the surface of CNC. FTIR analysis confirmed the formation of above hydrogen bonds. Scanning electron microscopy observations revealed good interfacial compatibility between CNC and PAA matrix. The nanocomposite hydrogels exhibited decreasing swelling ratio with increasing CNC-g-PAM content. Uniaxial tensile tests and tensile loading-unloading tests showed that elastic modulus, breaking strength and elongation at break of the nanocomposite hydrogels were significantly increased compared to PAA hydrogel, and that the nanocomposite hydrogels exhibited good self-recovery ability after large deformation.
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PMID:Fabrication of mechanically tough and self-recoverable nanocomposite hydrogels from polyacrylamide grafted cellulose nanocrystal and poly(acrylic acid). 3009 78