NMR investigations into heterogeneous structures of thermosensitive microgel particles

Abstract

The internal properties of submicron poly(N‐isopropylmethacrylamide) latex particles were investigated as a function of the methylene bisacrylamide (MBA) concentration used as a crosslinker. Two experimental approaches were performed. First, quasi‐electric light scattering measurements provided the size variation of the particles as a function of temperature, from which the swelling capacity of the particles as a function of MBA were estimated. In addition, the broadening and lowering effects of the volume phase transition temperature were detected from the turbidity of the solutions versus the MBA concentration. Second, observations of the transverse relaxation of protons gave evidence for heterogeneous structures inside the particles; several structural parts were discriminated from one another from different proton mobilities detected through magnetic relaxation rates. Corresponding to the concentration gradients of the crosslinker, the internal particle structures were looser and looser from the core to the shell. The state of the gelation of the polymer particles was governed by the initial amount of the crosslinker introduced into the latex recipe. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 889–898, 2000

Characterizing charge and crosslinker distributions in polyelectrolyte microgels

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Heterogeneous Morphology of Random Copolymer Microgels as Reflected in Temperature‐Induced Volume Transition and1H High‐Resolution Transverse Relaxation NMR

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“…The fi ts with two exponential functions [ Equation(17) ] are shown by solid lines and have χ 2 ≈ 0.0011 and correlation coeffi cients of R 2 ≈ 0.9911.…”

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