Sono-respond on thermosensitive polymer microgels based on cross-linked poly(N-isopropylacrylamide-co-acrylic acid)

Abstract

Ultrasound (US) exposure strongly influenced thermosensitivity of microgels attracted with both N-isopropylacrylamide (NIPAM) and acrylic acid (AA) segments, due to that hydrogen bonds of carboxylic acid segments in microgels were broken by US and then the hydration with water occurred. US induced critical effects on the volume phase transition temperature of the swelled NIPAM gel (PNAM). It was observed after the US exposure that the particle size was increased and the phase transition of the microgels shifted toward larger temperature regions of the hydrodynamic diameter. FT-IR spectroscopic data of the swelled microgel showed that the free OH stretching band intensity of the COOH segments was enhanced by the exposure, but the band intensity returned to its original level without the US exposure. This meant that the US stimulus broke hydrogen bonding of the microgel and induced hydration of water in the hydrogel environment. Finally, regeneration of the hydrogen bonds in the microgel was occurred after the US exposure.

Development of pH- and temperature-sensitive microgel particles: synthesis monitoring, characterisation and application as potential oral carriers.

“…It is important to emphasise that some sets represent preliminary tests with the purpose of knowing the system and verify the reproducibility, as well as to compare the results with the literature . Other set of experiments were planned according to an experimental design (Full and Fractional Factorial Experiment) based on the preliminary results and other literature KRATZ;HELLWEG;EIMER, 2000;VENEGAS-SANCHEZ et al, 2013) (Table 4.1). Table 4.1 shows all the assays used in this work.…”

(Micro)spectroscopy investigations of the properties of soft colloidal particles and perovskite materials

“…The crosslinker monomer, BA, consumes much faster than NIPAm 28 , thus the crosslinking density is decreasing from the surface to the center of a particle. The size and distribution of the microgel particles can be characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in the dry state, and dynamic light scattering (DLS) 1,29 , small-angle neutron scattering (SANS) 30 ,and laser diffraction particle distribution instrument 16 in the hydrated state.…”

“…Apart from the traditional stimulations, ultrasound exposure has recently been found to efficiently break the internal hydrogen bond and elevate the phase transition temperature of pNIPAm-co-AAc microgel (Figure 1.6) 16 . Reprinted with permission from Polymer Journal 16 (US is ultra-sound).…”

“…Since the first published account of thermo-sensitive poly(N-isopropylacrylamide) microgels in 1986 12 , pNIPAm-based microgels have attracted increasing amounts of attentions from scientists due to their potential use in both academic and industrial fields. The multi-sensitive properties of pNIPAm make it possible to tune their size by changing the ionic strength 13 , pH 14 , temperature 15 , ultrasound 16 and solvent composition 17 , which enriches the particle behaviors during phase transition.…”

“…As the size of pNIPAm particles can be tuned by external conditions such as pH 14 , temperature 15 and ultrasound 16 , the suspension exhibits flexible and controllable behaviors during phase transitions. Pelton et al 12 were the first to report on the formation of ordered loosely packed two-dimensional (2D) colloidal crystals based on pNIPAm microgels with a constant interparticle distance 80 .…”