Synthesis of Graphene Oxide-Polystyrene Graft Polymer Based on Reversible Addition Fragmentation Chain Transfer and Its Effect on Properties, Crystallization, and Rheological Behavior of Poly (Lactic Acid)

Li Yang,Weijun Zhen

doi:10.1155/2020/9364657

Abstract

Graphene oxide-polystyrene graft polymer (SGO-PS) was prepared by reversible addition-fragmentation chain transfer radical polymerization method. Orthogonal experiments indicated that the optimum synthesis reaction conditions for SGO-PS were as follows: the millimole ratio of chain transfer agent to initiator was 0.15 : 0.3, and the amount of styrene was 8 mL at 80°C for 12 hours. The products were characterized by Fourier transform infrared spectroscopy and thermal weightlessness analysis, and the highest grafting rate of SGO-PS was 62.46%. Then, PLA/SGO-PS nanocomposites were prepared using SGO-PS as fillers by melt intercalation method, and its crystallinity, mechanical properties, and thermal stability were significantly improved. Compared with pure PLA, the crystallinity of PLA/SGO-PS (0.3 wt%) nanocomposites was increased by 5 times. Multiple melting behavior tests showed that the introduction of SGO-PS caused the PLA molecular chain to be discharged into the unit cell in time, and the melting temperature shifted to a higher temperature, which ultimately made the grain structure of PLA composites more complete and stable than pure PLA. The rheological performance test showed that the uniform dispersion of SGO-PS in the PLA matrix inhibited the free movement of the PLA molecular chain and caused higher flow resistance, resulting in an increase in the complex viscosity, storage modulus, and loss modulus of PLA/SGO-PS.

Highlights

Plastic materials have been widely used in all aspects of life and industry
A modified graphite oxide (SGO) capable of initiating reversible addition-fragmentation chain transfer (RAFT) polymerization was prepared by the esterification reaction between the hydroxyl groups on the surface of Graphene oxide (GO) and a chain transfer agent
Fourier transform infrared spectrum (FTIR) and Thermal gravimetric analysis (TGA) tests showed the structure of the product, which confirmed that polystyrene was grafted to the surface of GO by RAFT polymerization, and the maximum grafting amount was 62.46%

Summary

Introduction

Plastic materials have been widely used in all aspects of life and industry. most conventional plastics are nonbiodegradable, and their accumulation in the environment has threatened the ecological balance of the earth [1]. The surface of GO has a large number of oxygen-containing functional groups, such as carboxyl (-COOH), hydroxyl (-OH), and epoxy functional groups (C-O-C) [22] These polar groups can make the polymer embedded in the graphene oxide layer to form a poly (lactic acid) nanocomposite, thereby effectively improving the mechanical properties of the polymer composite, the thermal properties, and the crystalline properties. A wide range of chain transfer agents for RAFT polymerization of alternative trithioesters can be used to prepare a series of homopolymers with different and narrow molecular mass distribution, which can be applied to the modification properties of GO to greatly expand the application of GO in the field of polymer composites. The effect of SGO-PS on properties, crystallization, and rheological behavior of poly (lactic acid) was investigated, respectively

Experimental

Characterization

Results and Discussion

Conclusion