A microcosm experiment was conducted at two phases in order to investigate the ability of indigenous consortia alone or bioaugmented to degrade weathered polystyrene (PS) films under simulated marine conditions. Viable populations were developed on PS surfaces in a time dependent way towards convergent biofilm communities, enriched with hydrocarbon and xenobiotics degradation genes. Members of Alphaproteobacteria and Gammaproteobacteria were highly enriched in the acclimated plastic associated assemblages while the abundance of plastic associated genera was significantly increased in the acclimated indigenous communities. Both tailored consortia efficiently reduced the weight of PS films. Concerning the molecular weight distribution, a decrease in the number-average molecular weight of films subjected to microbial treatment was observed. Moreover, alteration in the intensity of functional groups was noticed with Fourier transform infrared spectrophotometry (FTIR) along with signs of bio-erosion on the PS surface. The results suggest that acclimated marine populations are capable of degrading weathered PS pieces.

We present a comprehensive experimental rheological dataset for purified entangled ring polystyrenes and their blends with linear chains in nonlinear shear and elongation. In particular, data for the shear stress growth coefficient, steady-state shear viscosity, and first and second normal stress differences are obtained and discussed as functions of the shear rate, as well as molecular parameters (molar mass, blend composition, and decreasing molar mass of linear component in the blend). Over the extended parameter range investigated, rings do not exhibit clear transient undershoot in shear, in contrast to their linear counterparts and ring-linear blends. For the latter, the size of the undershoot and respective strain appear to increase with the shear rate. The universal scaling of the strain at overshoot and fractional overshoot (the ratio of the maximum to the steady-state shear stress growth coefficient) indicates subtle differences in the shear-rate dependence between rings and linear polymers or their blends. The shear thinning behavior of pure rings yields a slope nearly identical to predictions (−4/7) of a recent shear slit model and molecular dynamics simulations. Data for the second normal stress difference are reported for rings and ring-linear blends. While N2 is negative and its absolute value stays below that of N1, as for linear polymers, the ratio –N2/N1 is unambiguously larger for rings compared to linear polymer solutions with the same number of entanglements (almost by a factor of 2), in agreement with recent nonequilibrium molecular dynamics simulations. Furthermore, –N2 exhibits slightly weaker shear rate dependence compared to N1 at high rates, and the respective power-law exponents can be rationalized in view of the slit model (3/7) and simulations (0.6), although further work is needed to unravel the molecular original of the observed behavior. The comparison of shear and elongational stress growth coefficients for blends reflects the effect of ring-linear threading, which leads to significant viscosity enhancement in elongation. Along the same lines, the elongational stress is much larger than the first normal stress in shear, and their ratio is much larger for rings and ring-linear blends compared to linear polymers. This confirms the interlocking scenario of rings and their important role in mechanically reinforcing linear matrices.

The design and synthesis of new biomaterials with adjustable physicochemical and biological properties for tissue engineering applications have attracted great interest. In this work, chitosan-graft-poly(l-lactide) (CS-g-PLLA) copolymers were prepared by chemically binding poly(l-lactide) (PLLA) chains along chitosan (CS) via the “grafting to” approach to obtain hybrid biomaterials that present enhanced mechanical stability, due to the presence of PLLA, and high bioactivity, conferred by CS. Two graft copolymers were prepared, CS-g-PLLA(80/20) and CS-g-PLLA(50/50), containing 82 wt % and 55 wt % CS, respectively. Degradation studies of compressed discs of the copolymers showed that the degradation rate increased with the CS content of the copolymer. Nanomechanical studies in the dry state indicated that the copolymer with the higher CS content had larger Young modulus, reduced modulus and hardness values, whereas the moduli and hardness decreased rapidly following immersion of the copolymer discs in alpha-MEM cell culture medium for 24 h. Finally, the bioactivity of the hybrid copolymers was evaluated in the adhesion and growth of MC3T3-E1 pre-osteoblastic cells. In vitro studies showed that MC3T3-E1 cells exhibited strong adhesion on both CS-g-PLLA graft copolymer films from the first day in cell culture, whereas the copolymer with the higher PLLA content, CS-g-PLLA(50/50), supported higher cell growth.