Nanogels and microgels: The new polymeric materials playground

Abstract

Microgels, or intramolecularly crosslinked macromolecules (ICMs), have been known for a number of years. They are formed during the polymerization of polyfunctional precursors en-route, but at incomplete reaction, to the macrogelation predicted by the theories of gelation initially propounded by Carothers and Flory. These gelation theories did not predict that such microgels made in solution could be prepared from such polyfunctional reactive solutions at complete reaction and high concentrations, without gelation. Microgels have been successfully and usefully prepared, however, at complete conversion of their contained reactive groups by the use of either aqueous or non-aqueous dispersion polymerization in which surface active agents are utilized to contain the polymerization to isolated submicron-size domains. The progression towards macrogelation is constrained to the maximum size of the dispersed domains. This paper demonstrates the contrasting general observation that macrogelation in solvents of such polyfunctional reactive precursors cannot occur below a Critical Gelation Concentration (CGC) if a carefully selected match of solvent solubility parameters for the polymerization solvent and the formed polymer is made. In some cases the addition of only ca. ten percent wlw of solvent is required to completely prevent macrogelation at complete conversion. In addition polymerization the molecular weight of the produced ICMs may be varied in a simple controllable manner from the low thousands (nanogels) to many millions (microgels) simply by the choice of concentration at which they are prepared. The products are a distinct form of polymer which is quite different to the linear analogue and almost certainly these solution-prepared products are different to the microgels formed by aqueous dispersion polymerization techniques. This new solution technique provides a simple and general new method for the ready synthesis and design of an enormous range of bespoke globular polymers having both fundamental academic interest and potential commercial utility.

Transport of Indomethacin from Kappa-Carrageenan based Nanogel

“…The amount of drug dissolved was determined spectrophotometrically at 266 nm (UV-1601PC, Shimadzu, Japan). Entrapment efficiency EE (%) was calculated using equation (1).…”

“…Hydrogel nanoparticle is known as nanogel and can be used flexibly to provide new therapeutic strategies for autoimmune diseases and degenerative diseases [1][2][3]. Hydrogels are polymeric networks having three dimensional configurations and have the ability to imbibe and retain water within their structural moiety [4].…”

“…Hydrogels are polymeric networks having three dimensional configurations and have the ability to imbibe and retain water within their structural moiety [4]. These gels at nanoscale level have gained considerable attention as drug delivery carriers [1]. Properties of nanogel such as bioavailability, large surface area for multivalent bioconjucation, diameter, mechanical property, size for specific purpose make it a good candidate for drug delivery systems [4].…”

Novel macroporous amphoteric gels: Preparation and characterization

“…When the size of microgels is in the submicron range, they are known as nanogels [2]. According to the IUPAC definition, materials having pores of larger than 50 nm are called macroporous [3].…”

Hydrogel Microparticles as an Emerging Tool in Pharmaceutical Field: A Review

“…When the size of microgels is reduced up to the range of submicrmeters, they are known as nanogels. [5][6][7] Microgels/nanogels offer unique advantages for polymer-based drug delivery systems (DDS) over polymer protein conjugates, 8 polymer-drug conjugates, 9,10 micelles, [11][12][13] and vesicles 14,15 based on amphiphilic and doubly hydrophilic block copolymers, dendrimers, 16 and submicrometer-sized particulates. 17,18 Microgels/nanogels' size range from nanometers to several micrometers with a large surface area for conjugation with drugs.…”