PNIPAM samples

Au NPs protected with a thermo-responsive polymer such as PNIPAM by the covalent grafting to technique with different end-functional PNIPAMs and various ratios between PNIPAM and HAuC14 has been studied. PNIPAM samples were synthesized through either conventional radical polymerization or living/controlled radical polymerization. With this approach, very small and quite monodisperse Au NPs are obtained with diameters ranging from 1.5 to 2.3 nm [94]. 

Fig. 3 Dissolving kinetics (in terms of average hydrodynamic radius Rh) of collapsed single-chain PNIPAM globules, where t is the standing time after the solution temperature was quenched from 33.02 to 30.02 °C and the dashed line represents a stable average value of Rh of individual PNIPAM random coils at 30.02 °C. The weight-average molar mass (Mw) of the PNIPAM sample used is 1.08 x 107g/mol with a polydispersity index (Mw/Mn) less than 1.1 [32]...

Fig. 4 Plot of static expansion factor (as) as a function of relative temperature 0/T, where a is defined as Rg(T)/Rg((9) symbols are our measured results and the lines are calculated data with three different values of r. If choosing M = 113 (molar mass of monomer NIPAM), we have r 105 for both the PNIPAM samples used [32]...

FIG. 22 Temperature behavior of the structural parameters of a PEC between ionically modified PNIPAM samples AIFL 2 and AIFL 3 (X = 0.6 AIFF 2 in excess, 0.01 M NaCl). 

Tg (-22 °C) of a homogeneous 70/30 PNIPAM-water mixture. Observation of samples by scanning electron microscopy and optical microscopy revealed that the morphology of the polymer-rich phase is preserved only if the polymer solutions are brought to zone C. Polymer solutions heated to zone B undergo demixing upon quench-cooling [160]. Aqueous solutions of PVCL, PNIPMAM, and PNIPMA exhibit similar behaviour [157,158,369,370]. 

Sample (NIPA) MAI 1900 MAI550 Solvent Mn(PNIPAM) NIPAM/EO°... 

Figure 4. Temperature dependence of the PNIPAM colloid diameter and turbidity. The diameter was determined using a commercial quasielastic light scattering apparatus (Malvern Zetasizer 4). The turbidity was measured for a disordered dilute dispersion of these PNIPAM colloids by measuring light transmission through a 1.0 cm pathlength quartz cell with a UV-visible-near IR spectrophotometer. Solids content of the sample in the turbidity experiment was 0.071%, which corresponds to a particle concentration of 2.49 x 10 spheres/cc. Also shown is the temperature dependence of the turbidity of this random colloidal dispersion. The light scattering increases as the particle becomes more compact due to its increased refractive index mismatch from the aqueous medium (76) (Adapted from ref 16).

Figure 6. Temperature tuning of Bragg diffraction from a 125-p,m-thick PCCA film of 99-nm polystyrene spheres embedded in a PNIPAM gel. The diffraction wavelength shift results from the temperature-induced volume change of the gel, which alters the lattice spacing. Spectra were recorded in a UV-visible-near IR spectrophotometer with the sample placed normal to the incident light beam (Adapted from ref 16).

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