Crosslinking of water-soluble pullulan nanofibrous mats through atmospheric plasma treatment

Summary form only given. Water soluble polymers may display interesting properties (e.g. thermal, mechanical, biocompatibility, etc.) that make them useful in different fields where, however, the stability of the material in a aqueous environment is often required. Chemical modification of the polymer molecular chains are commonly applied to introduce interchain bridging (crosslinks) that impart water resistance to the material. However, these methods are time-consuming and often make use of toxic chemical agents. Recently, it has been reported that non-equilibrium plasma treatments, commonly used to modify the chemical structure and the reactivity of polymer surfaces, are able to induce formation of radicals, which may recombine, producing unsaturation and crosslinking
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. In this work we focus on the use of atmospheric pressure non-equilibrium plasmas to crosslink pullulan. Pullulan is a water soluble polysaccharide whose biodegradability, biocompatibility, low oxygen permeability and high temperature resistance make it very attractive for food technology, pharmaceutical application, environmental remediation and filtration. Results will be presented concerning the treatment of pullulan in form of electrospun mat with a Dielectric Barrier Discharge plasma source, inserted in a properly designed chamber, operated in environment air at atmospheric pressure and driven by a HV amplifier connected to a function generator with a microsecond rise time. In order to evaluate the effects of electrical parameters and treatment time on the degree of crosslinking in pullulan, several operating conditions were investigated. The crosslinking degree of plasma treated electrospun samples was evaluated: (i) from the capability of the pullulan fibers to preserve their morphology upon water exposure; (ii) through weight loss and swelling degree measurements; (iii) by monitoring the change of mechanical properties of electrospun mat after plasma treatment.Results show a relevant enhancement of electrospun pullulan mats water resistance after plasma treatment, demonstrating that this treatment is an environmental friendly crosslinking approach. First conclusions on the correlation between plasma operating parameters and crosslinking degree will be presented. The in situ one-step crosslinking by plasma can be easily extended to other water-soluble polymers.