Degradable microgels synthesized using reactive polyvinylalkoxysiloxanes as crosslinkers

Abstract

In the present work we demonstrate the synthesis of degradable thermo-sensitive poly(N-vinylcaprolactam) microgels via precipitation polymerization using reactive polyvinylalkoxysiloxanes as crosslinkers (Cross-PAOS). These compounds were synthesized by co-condensation of vinyltriethoxysilane and tetraethoxysilane followed by transesterification with poly(ethylene glycol) monomethyl ether (PEG) to increase their water solubility. Experimental results showed that the microgels synthesized using Cross-PAOS exhibited excellent colloidal stability in water. These microgels are thermo-responsive and their size can be tuned depending upon the ratio of vinyl and PEG groups in Cross-PAOS. The size of microgel particles increases with increasing vinyl groups in Cross-PAOS while it decreases with increasing PEG groups. The presence of silicon dioxide in the microgel structure was confirmed by X-ray photoelectron spectroscopy and elemental analysis. Additionally, the microgels prepared in this way contain crosslinking sites which can be degraded under alkaline conditions.

Poly(N-vinylcaprolactam), a comprehensive review on a thermoresponsive polymer becoming popular

“…The most widely used crosslinker for micro/nanogels is BIS [47,152,162,165,172,173,175,176,178,179,182,[184][185][186][187]189,192,193,195,198,200]; while other crosslinkers were also used: N,Nbis(acryloyl) cystamine (BAC) [178], poly(ethylene glycol) diacrylate (PEGDA)…”

“…The most widely used initiators considering all methods of synthesis of PNVCL micro/nanogels are: hydrogen peroxide and L-ascorbic acid as redox initiators [48]; 2,2'-azobis(2-methylpropioamidine) dihydrochloride (AMPA) as thermal azo-initiator [152,172,173,[184][185][186]189,192,198]; 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] (ACMA) [162,199], 2,2'-azobis (N,N'-dimethyleneisobutyramidine) dihydrochloride (ADIBA) [195], potassium persulfate [47, 165, 175, 177-179, 182, 187, 193,200-202,], ammonium persulphate (APS) [197], 2,2-azobis [2-methyl-N-(2-hydroxyethyl) propionamidine] (VA-086) [193], and tert-butyl hydroperoxide (TBHPO) [202], as thermal peroxide initiators ( Figure 15). The most widely used crosslinker for micro/nanogels is BIS [47,152,162,165,172,173,175,176,178,179,182,[184][185][186][187]189,192,193,195,198,200]; while other crosslinkers were also used: N,Nbis(acryloyl) cystamine (BAC) [178], poly(ethylene glycol) diacrylate (PEGDA)…”

Supramolecular Stimuli‐Responsive Microgels Crosslinked by Tannic Acid

“…The microgels were synthesized by radical precipitation polymerization in aqueous medium, using the tannic acid as a novel physical crosslinker. So far, classical crosslinking agents with polymerizable groups were used for the synthesis of PVCL based microgels . Our synthesis method provides a novel approach for the design of stimuli‐responsive degradable microgels with a broad spectrum of structural properties and functionalities.…”

Functional Microgels: Recent Advances in Their Biomedical Applications

“…A series of siloxane‐based crosslinkers were developed by Agrawal et al for the synthesis of degradable PVCL microgels . The size and volume phase transition temperature of these microgels could be tuned depending upon the ratio of vinyl and PEG groups in siloxane crosslinker.…”

“…PNIPAM‐ and PVCL‐based microgel particles are the two most commonly investigated candidates among temperature‐responsive microgels . These microgels show a volume phase transition temperature (VPTT) above which the particles collapse drastically due to increased polymer–polymer interactions, thus releasing the encapsulated drug .…”