Swelling control in thermo-responsive hydrogels based on 2-(2-methoxyethoxy)ethyl methacrylate by crosslinking and copolymerization with N-isopropylacrylamide

Abstract

Two different strategies were used to modulate the swelling capacity of thermo-responsive hydrogels based on 2-(2-methoxyethoxy)ethyl methacrylate (MEO 2 MA) in water. In the first approach, several poly(MEO 2 MA) hydrogels were synthesized using different proportions of a conventional crosslinker, as tetra(ethylene glycol) dimethacrylate and a non-conventional inorganic crosslinker, as polyhedral oligomeric silsesquioxane (POSS) functionalized with eight methacrylic groups (POSS-meth 8 ). The experiments showed that the equilibrium swelling and the volume transition temperature (VTT) could be tuned by varying the crosslinker degree, regardless of the type of crosslinker. In the second approach, several poly (MEO 2 MA-co-N-iPAAm) hydrogels were prepared for the very first time, because N-isopropylacrylamide (N-iPAAm) is also a thermo-responsive component that increases the swelling capacity of the hydrogel in water. In addition, the VTT and the glass transition temperature of these new copolymer hydrogels could also be tuned by varying the monomeric composition. Polymer Journal (2011) 43, 887-892; doi:10.1038/pj.2011.83; published online 31 August 2011Keywords: 2-(2-methoxyethoxy)ethyl methacrylate; N-isopropylacrylamide; polyhedral oligomeric silsesquioxane; tetra(ethylene glycol) dimethacrylate; thermo-responsive hydrogels; volume transition temperature INTRODUCTION Thermo-responsive hydrogels undergo relatively large and abrupt volume changes in response to temperature. 1-3 Among these materials, N-isopropylacrylamide-based (N-iPAAm) hydrogels are the most studied 4,5 because poly(N-iPAAm) shows a well-defined lower critical solution temperature in water at around 31-34 1C, 6-8 which is close to body temperature. Thus, such stimuli-sensitive hydrogels have been intensively studied with respect to drug delivery 9,10 and other biomedical applications. [11][12][13][14][15][16][17] Recently, hydrogels based on oligo(ethylene glycol) side chains methacrylic monomers, 18-22 such as 2-(2-methoxyethoxy)ethyl methacrylate (MEO 2 MA), were highlighted as a successful alternative to poly(N-iPAAm)-based hydrogels because of the advantages of a controllable lower critical solution temperature, 23,24 high biocompatibility/ low cytotoxicity 25,26 and facile polymerization by both the free radical and the anionic polymerization mechanisms. 27 The previous investigations on MEO 2 MA-based hydrogels were mainly focused on controlling the thermo-responsive behavior for biomedical applications. For instance, they have been synthesized by controlled radical polymerization techniques, such as atom transfer radical polymerization, to create more homogeneous networks. 28 In other cases, they have been copolymerized with ionic monomers to obtain additional pH responsiveness. 20,22

On Going to a New Era of Microgel Exhibiting Volume Phase Transition

“…Precipitation polymerization using degradable cross-linkers is another way to prepare disposable microgel [61,62].…”

Controlled release of bupivacaine using hybrid thermoresponsive nanoparticles activated via photothermal heating

“…1c showed the characteristic band at 2880 cm -1 attributed to C-H stretching vibrations [54]. The peak at 1720 cm -1 was assigned to the stretching vibration of C=O groups in the polymer, and the broad band at 1109 cm -1 corresponds to C-O-C stretching vibrations [55]. 1 H-NMR and FTIR signals in Fig.…”

“…Therefore the modified nanoparticles could be activated by 808nm-NIR laser irradiation to generate the heat required to activate the phase transition of the polymer (Fig. 3c), the broad band at 1109 cm -1 corresponds to the C-O-C stretching vibration and the 1720 cm -1 peak was ascribed to the stretching vibration of the C=O group of the polymer [55]. The stability of the…”

Thermoresponsive Gold Polymer Nanohybrids with a Tunable Cross‐Linked MEO2MA Polymer Shell

“…However, further research is required to establish the enhanced biocompatibility of these coatings. Copolymers based on MEO 2 MA show a lower critical solubility temperature (LCST) close to room temperature, above which there is an abrupt collapse of the polymer . In addition, the LCST can be modulated by copolymerization of MEO 2 MA with longer OEG methacrylates hence providing the potential to fine‐tune the LCST without introducing comonomers of a different chemical nature .…”