Multifunctional Polypyrrole-silver Coated Layered Double Hydroxides Embedded into a Biodegradable Polymer Matrix for Enhanced Antibacterial and Gas Barrier Properties

In this study,polypyrrole-silver coated layered double hydroxides(LDHs@PPy-Ag)was prepared by chemical polymerization of pyrrole(Py)with silver ions.Silver nanoparticles(AgNPs)could be uniformly reduced onto PPy coatings in situ by redox reaction during simultaneous polymerization process.And LDHs@PPy-Ag/poly(ε-caprolactone)(PCL)nanocomposites were fabricated by solution casting method.It is revealed that spherical AgNPs are loaded on PPy coatings uniformly.Particularly,compared with pure PCL,LDHs@PPy-Ag/PCL nanocomposites with incorporation of only 1 wt%LDHs@PPy-Ag show a 17%increase in tensile strength(36.5 MPa)and a 29%increase in elongation at break(822%).Upon PPy-Ag coatings onto original LDHs,oxygen relative permeability of LDHs@PPy-Ag/PCL nanocomposites decreases to 52%with the same addition.Meanwhile,due to the double antibacterial activity of PPy and AgNPs,the antibacterial rate of LDHs@PPy-Ag reaches 100%.And the corresponding LDHs@PPy-Ag/PCL nanocomposites also show outstanding antibacterial activity.Considering the superiority of their comprehensive performance,antibacterial LDHs@PPy-Ag/PCL nanocomposites can be used further for the application as biodegradable polymeric active packaging materials.

Superior Ductile and High-barrier Poly(lactic acid)Films by Constructing Oriented Nanocrystals as Efficient Reinforcement of Chain Entanglement Network and Promising Barrier Wall

It is a daunting task to develop a promising strategy at an industrial scale for simultaneously ameliorating ductility and gas barrier performance of poly(lactic acid)(PLA)films in the application of green packaging.In this work,biaxial stretching and constrained annealing were employed to prepare transparent PLA films with superior ductility and barrier properties.The oriented nano-sized crystals induced by biaxial stretching were developed into regularαform during constrained annealing,which could not only serve as“nano-barrier wall”to impede the diffusion and dissolution of gas molecules,but also strengthen amorphous chain entanglement network as physical crosslink to enhance ductility.As a result,the as-prepared PLA films exhibited an outstanding comprehensive performance with a low oxygen and water vapor permeability coefficient of 0.733×10^(-14) cm^(3)·cm·cm^(-2)·s^(-1)·Pa^(-1) and 3.82×10^(-14) g·cm·cm^(-2)·s^(-1)·Pa^(-1),respectively,outstanding ductility with elongation at break of 66.0%,high yield strength of 84.2 MPa,and good transparency of more than 80%at 550 nm.The new insight in the relationship between microscopic amorphous and crystalline structure and macroscopic performance is conducive to alleviating the intrinsic defects of brittle and insufficient barrier PLA films without the aid of any heterogenous modifiers,facilitating their widespread commercialization in the booming sustainable packaging market.