PNIPAM microgels

Fig. 16 Temperature dependence of average hydrodynamic radius (< Rh)) and average radius of gyration Pg of PNIPAM microgels grafted with linear PEO chains in the heating-and-cooling cycle, where the dispersion concentration is 1.0 x 10 5 g/mL [70]...

Fig. 17 Dependence of the average PEO brush height ((Jj)brush) on the surface area per grafted chain (s), where (/i)brush was calculated by two different methods. The squares represent (h)brush from the difference between the average radii of the PNIPAM microgels with and without the grafted PEO chains and the circles from the ratio of / [70]...

For example, surfaces comprising PNIPAM microgels were utilized for drug delivery [138], Electrostatic layer-by-layer assembly with poly(NIPAM-coacrylic acid) and poly(allylamine hydrochloride) on an amino-functionalized surface yielded thermoresponsive thin films. These were capable of a thermally regulated uptake and release of the chemotherapeutic drug doxorubicin. The films were loaded... 

Wong IE, Gaharwar AK, Muller-Schulte D, Bahadur D, Richtering W (2008) Dual-stimuli responsive PNIPAM microgel achieved via layer-by-layer assembly magnetic and thermore-sponsive. 1 Colloid Interface Sci 324 47-54... 

FIGURES Radius of gyration for PNIPAM microgels in aqueous solution (solid squares) and after addition of mass fraction 0.4 of Fe Oj nanoparticles, data after Rubio-Retama et al. (2007). 

Figure 1 SEM image of single poly(/V-isopropylactylamide) (PNIPAM) microgel particle.

Pelton and co-workers showed that the size of PNIPAM microgels decreases by a factor of 10 if sodium dodecyl sulfate (SDS) was used in the polymerization procedure. Lyon s group used SDS for stabilization of PNIPAM microgels prepared with PEG diacrylates of different PEG chain length. ... 

To investigate the influence of polymerization conditions on internal structure of PNIPAM microgels, SDS was used in batch and semibatch polymerization processes. 

Bianco-Peled et have studied the binding of proteins (BSA, ovalbirmin, and LZ) to PNIPAm microgels to understand the relation between the binding charaaeristics and the... 

Figure 23 The structure of PNIPAM microgels. A highly cross-linked core is characterized by a radial box profile up to BboxThe cross-linking density decreases with increasing distance to the core and is described by asurf- At R, the profile has decreased to half the core density. The overall size obtained by SANS is approximately given by / sans = B + surf. where the profile approaches 0. Bsans is often slightly smaller than the hydrodynamic radius Ru obtained by DLS. Reused with permission from Stieger, M. Richtering, W. Pedersen, J. S. Lindner, P. J. Chem. Phys. 2004, 120, 6197-6206. Copyright 2004, American Institute of Physics.

Figure 30 Top normalized FTIR spectra of PNIPAM microgels in D2O at 50 °C and pressures from 1 to 10600 bar. The arrow indicates increasing pressure. Bottom scheme illustrating the antagonistic influence of temperature and pressure on the swelling of PNIPAM microgels.

Guan, Y Zhang, Y. J. PNIPAM microgels for biomedical applications from dispersed particles to 3D assemblies. Soft Matter 2011, 7, 6375-6384. 

Karg, M. Pastoriza-Santos, I. Perez-Juste, J. Hellweg, T. Liz-Marzan, L. M. Nanorod-coated PNIPAM microgels thermoresponsive optical properties. Small 2007, 3, 1222-1229. 

M. Karg et al.. Nanorod-coated PNIPAM microgels Thermore-sponsive optical properties. Small, 3(7), 1222-1229 (2007). 

Figure 6 (a) Interaction potentials between colloidal silica spheres and a silica wall with gravitational contribution subtracted. Symbols are experimental data and full lines are least squares fits by a superposition of electrostatic repulsion and depletion attraction introduced by a temperature-sensitive PNIPAM microgel. The potential depth increases with decreasing temperature (top most curve 29 °C bottom curve 20 °C). (b) Video microscopy images of the silica colloids observed at 29 °C (i) and 20 °C (ii). Reproduced with permission from Fernandes, G. E. Beltran-Villegas, D. J. Sevan, M. A. LangmuirZOOZ, 24,1077. ... 

As mentioned above, the cross-link density in PNIPAM microgels will decay to the surface and the particle will be characterized by a fuzzy, smeared surface as schematically displayed in Figure 16. The form factor can be determined by scattering methods and the fuzziness of the particle surface... 

Figure 18 Size of PNIPAM microgels with different cross-linker content (increasing from top to bottom) vs. temperature. Reproduced with permission from Figure 1 in Senff, H. Richtering, W. ColloidPolym. Sci. 2000, 278, 830. ...

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