Gas permeable membranes composed of carboxylated poly(vinyl chloride) and polyurethane

Gas-permeable polymeric membranes containing carboxyl groups which are suit able for enzyme immobilization were investigated in order to use them as ga s electrode membranes in biosensors. Carboxylated polyurethane (CPU) was sy nthesized via a reaction between 2,2-bis(hydroxymethyl)propionic acid as a chain extender and prepolymers prepared from polycarprolactone (Mn=2,000) a nd 4,4'-diphenylmethane: diisocynate. It was difficult to prepare membranes from the pure CPU because of its high elasticity and cohesion. However, tr ansparent foe-standing membranes were easily prepared from the blend soluti ons of CPU and carboxylated poly(vinyl chloride) (CPVC) in tetrahydrofuran. Both elasticity and cohesion of the CPU/CPVC membranes were decreased with increasing the content of CPVC. DSC experiment suggests that CPU and CPVC may be well mixed. Permeability coefficients for O-2 and CO2 (P-O2 and P-CO 2) in the membranes increased as the proportion of CPU increased. The addit ion of dioctyl phthalate (DOP), a plasticizer, significantly enhanced the P -O2 and P-CO2 which were 4.4 and 30 Barrer, respectively, in the CPU/CPVC ( 80/20 wt/wt) tl membranes containing 20% of DOP at 25 degrees C and 100 psi . Thus this type of membranes may have a potential for the use as gas elect rode membranes in biosensors.