Polymer Grafting Onto Polyurethane Backbone Via Diels-Alder Reaction

Abstract

Biocompatible, biodegradable, or bioresorbable polymers are constantly being used in biomedical and environmental applications, such as medical implants or drug-delivery systems. In terms of finding new technologies with the capability of having environmental friendly materials, it is paramount to seek new ways of improving the functionalities of polymers such as polyurethanes in this case. For that matter, since polyurethanes are an important class of polymers in the field of academy and industry, the development in that area would serve mankind a spectacular application branches in the field of medicine, autos, coatings, paintings and adhesives. Aliphatic polyurethane with pendant anthracene moieties (PU-anthracene) were prepared from polycondensation of anthracen-9-yl methyl 3-hydroxy-2-(hydroxymethyl)-2-methylpropanoate (anthracene diol) 1, with hexamethylenediisocyanate (HMDI) in the presence of dibutyltindilaurate (DBTL) in CH2Cl2 at room temperature for 10 d. Aliphatic polyurethane with a pendant anthracene group is employed as a backbone. The graft copolymers with regular graft points containing PU backbone combed with poly(methyl methacrylate) (PMMA) and poly(ethylene glycol) (PEG) side chains were simply achieved by a sequential polymer click reactions. The PU-anthracene (Mn,GPC = 12900 g/mol, Mw/Mn= 1.87, relative to PS standards) was clicked with a linear α-furan protected-maleimide terminated-poly(methyl methacrylate) (PMMA-MI) (Mn,GPC = 2500 g/mol, Mw/Mn =1.33) , or –poly(ethylene glycol) (PEG-MI) (Mn,GPC = 550 g/mol, Mw/Mn = 1.09), to result in well-defined PU-graft copolymers, PU-g-PMMA (Mn,GPC = 23800 g/mol, Mw/Mn = 1.65, relative to PS standards) or PU-g-PEG (Mn,GPC = 11600 g/mol, Mw/Mn = 1.45, relative to PS standards) using Diels-Alder reaction in dioxane/toluene at 105 0C, have gained increasing interest for their potential use in biomedical and pharmaceutical applications due to their favorable biocompatibility, biodegradability, and nontoxicity. The Diels-Alder grafting efficiencies were found to be over 93-99% using UV spectroscopy. Moreover, the structural analyses and the thermal transitions of all copolymers were determined via 1H NMR, DSC and TGA, respectively. It was found out that all the graft structures including the model (PU-g-Adduct Alcohol, PU-g-PEG, PU-g-PMMA) were fitting with the results of 1H NMR, UV, DSC and TGA. With respect to the UV Diels-Alder efficiencies of those mentioned grafts were found to be in the range of 93 – 99 %. This vindicates the success of the yields of graft. In terms of technological aspects and future work, one can assume that, grafts onto Polyurethane backbone might have significant improvements in the stress vs strain graph. PMMA has the durability, PEG has the hydrophilicity and PU has the elasticity and toughness. When these are combined in the stress vs strain graph, an elastic, tough, strong, heat resistant (due to higher Tg points of DSC) combed like polymer structure is seen to be formed.