CLEAR NONIONIC POLYURETHANE HYDROGELS FOR BIOMEDICAL APPLICATIONS

Clear nonionic polyurethane hydrogels having a broad range of mechanic al properties and degrees of swelling were prepared by both bulk (comp ression molding) and solution polymerization processes. Hydrogels cont aining 70% water were also prepared which had an elongation of 1150% a nd a tensile strength of 280 kPa. The effects of the chemical structur e, molecular weight, and functionality of polyether polyols and type o f diisocyanate on hydrogel properties were studied. In addition, the t ype and concentration of crosslinker, and concentration of ethylene gl ycol, which was used as chain extender were investigated. In order to achieve transparency in the hydrogels, it was determined that poly(oxy propylene) glycols (PPGs) should be present in the system to disrupt t he crystallinity of the poly(oxyethylene) glycol (PEG) soft segments. The PEG segments of the network which contain the hydrophilic moiety a re responsible for the absorption of water. However, in addition to th e concentration of oxyethylene, the degree of swelling of the hydrogel s was also determined by measuring the elasticity of the polymer netwo rk. The elasticity of the polymer network is determined by the molecul ar weight between crosslinks (crosslink density) and the concentration of hard segments in the network. The concentration of hard segments w as controlled by the concentration of chain extender. The crosslink de nsity was controlled by the diol/triol ratio and the respective molecu lar weight of each component.