Chitosan is a well-known biodegradable biopolymer, which possesses antimicrobial properties. In this study, the effect of chitosan incorporation on the morphology; thermal, mechanical, and rheological properties; and antibacterial and photodegradation behaviors of polyethylene (PE)/thermoplastic starch (TPS) blends were examined. PE/TPS blends were compatibilized with low-density PE-grafted maleic anhydride copolymer (PE- g-MA) compatibilizer. Scanning electron microscopy (SEM) and tensile test indicated that the addition of chitosan in powder form has a devastating effect on both mechanical and morphological properties of the blends. Therefore, chitosan was plasticized with acetic acid and glycerol (2 wt% chitosan dissolved in acetic acid/glycerol solution) prior to addition to the blends, which considerably improved the mechanical properties of the blends. Dynamic rheological experiments revealed a decrease in the complex viscosity of the blends with the addition of plasticized chitosan compared with unplasticized chitosan. SEM micrographs demonstrated more homogenous microstructure for the blends containing plasticized chitosan and PE- g-MA compatibilizer. Differential scanning calorimetry results indicated that unplasticized chitosan acts as a nucleation agent for PE crystallization. Antibacterial analysis indicated that the incorporation of chitosan had a significant effect on preventing from bacterial population growth. The major part of this article was to study the effect of ultraviolet (UV) exposure on the chemical structure and mechanical properties of the blends, using Fourier transform infrared spectroscopy and tensile properties examination. The results indicated that the slight amount of chitosan may significantly improve the photostability of PE/TPS blends against UV degradation. However, PE- g-MA compatibilizer dramatically decreased the UV resistance of the blends.

Performing dynamic off-lattice multicanonical Monte Carlo simulations, we study the statics, dynamics, and scission–recombination kinetics of a self-assembled in situ-polymerized polydisperse living polymer brush (LPB), designed by surface-initiated living polymerization. The living brush is initially grown from a two-dimensional substrate by end-monomer polymerization–depolymerization reactions through seeding of initiator arrays on the grafting plane which come in contact with a solution of nonbonded monomers under good solvent conditions. The polydispersity is shown to significantly deviate from the Flory–Schulz type for low temperatures because of pronounced diffusion limitation effects on the rate of the equilibration reaction. The self-avoiding chains take up fairly compact structures of typical size R g(N) ∼ N ν in rigorously two-dimensional (d = 2) melt, with ν being the inverse fractal dimension (ν = 1/d). The Kratky description of the intramolecular structure factor F(q), in keeping with the concept of generalized Porod scattering from compact particles with fractal contour, discloses a robust nonmonotonic fashion with q d F(q) ∼ (qR g)−3/4 in the intermediate-q regime. It is found that the kinetics of LPB growth, given by the variation of the mean chain length, follows a power law ⟨N(t)⟩ ∝ t 1/3 with elapsed time after the onset of polymerization, whereby the instantaneous molecular weight distribution (MWD) of the chains c(N) retains its functional form. The variation of ⟨N(t)⟩ during quenches of the LPB to different temperatures T can be described by a single master curve in units of dimensionless time t/τ∞, where τ∞ is the typical (final temperature T ∞-dependent) relaxation time which is found to scale as τ∞ ∝ ⟨N(t = ∞)⟩5 with the ultimate average length of the chains. The equilibrium monomer density profile ϕ­(z) of the LPB varies as ϕ­(z) ∝ ϕ–α with the concentration of segments ϕ in the system and the probability distribution c(N) of chain lengths N in the brush layer scales as c(N) ∝ N –τ. The computed exponents α ≈ 0.64 and τ ≈ 1.70 are in good agreement with those predicted within the context of the Diffusion-Limited Aggregation theory, α = 2/3 and τ = 7/4.