Thermo- and pH-Responsive NT-Polymer Composites

Another example is the composites formed by poly(acryhc acid) (PAA)-modified SWNTs [93] the viscosity of these aggregate suspensions is responsive to pH. At low shear rates ( 100 s ) the viscosity increased as the pH rose from 2.9 to 9.2. 

The reversibility of these changes was observed when the pH of the suspension was reduced progressively from 9.2 to 2.9 this effect arises from the chemical and conformational changes in PAA that take place with changes in pH. 

Stable NT-lysozyme (LSZ) complexes can be obtained by dispersing NTs in an aqueous solution of LSZ (isoelectric point at pH 10.02) they exhibit pH-responsive properties [94]. The NT-LSZ remains in a highly dispersed state at pH 8 and at pH 11 (lysozyme highly charged), whereas in the pH range 8-11 (lysozyme not charged) the NT-LSZ aggregates become insoluble. The secondary and tertiary stmctures of most of the lysozyme are well preserved-a feature that holds promise for the development of NT-based biomedical devices. 

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