Synthesis of New Thiophene Derivatives and Their Use as Photostabilizers for Rigid Poly(vinyl chloride)

Asim A Balakit,Gamal A El-Hiti,Ahmed Ahmed,Emad Yousif,Keith Smith

doi:10.1155/2015/510390

Abstract

Five new thiophenes, namely,N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e), have been synthesized. All of these materials brought about a reduction in the level of photodegradation of poly(vinyl chloride) (PVC) films containing the synthesized thiophenes (0.5%; by weight). The results obtained showed that the extent of photostabilization of PVC in the presence of an additive was in the order4e > 4d > 4b > 4a > 4c. For the most favorable additive (4e), the rate of appearance of infrared absorption bands of degradation products was reduced by around two-thirds, while the quantum yield of chain scission was calculated to be reduced by a factor of more than one thousand. It is suggested that the additives may help stabilize PVC by direct absorption of UV radiation and dissipation of the energy as heat or that electrostatic attraction between the additives and PVC may assist transfer of energy from excited state PVC to the additive, from where it can be dissipated.

Highlights

Poly(vinyl chloride) (PVC) is second to polyethylene among the highest selling types of plastic materials, which are widely used in a wide range of industries including architecture, electronics, packaging, and transportation [1]
Ultimate user acceptance of the PVC products for outdoor building applications depends on their ability to resist photodegradation over long periods of sunlight exposure
The structures of the synthesized imines 4a–e were confirmed by FTIR, 1H NMR, and 13C NMR spectroscopy and by mass spectrometry (EI-MS and high resolution mass spectrometry (HRMS))

Summary

Introduction

Poly(vinyl chloride) (PVC) is second to polyethylene among the highest selling types of plastic materials, which are widely used in a wide range of industries including architecture, electronics, packaging, and transportation [1]. The low cost and the good performance of PVC products have increased the utilization of this polymer in building, mainly in exterior applications such as window profiles and cladding [2]. The PVC resin needs to be compounded and processed properly using suitable additives, leading to a complex material whose behavior and properties are quite different from those of the PVC resin itself [3]. It is important to perform reliable weathering methods to test factors, like light and temperature, which influence the degradation of PVC based materials in accelerated service conditions. We report the syntheses of various imines derived from thiophenes, namely, N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b), N-[(3bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e) and studies of their activity in the photostabilization of PVC. To the best of our knowledge this is the first attempt to investigate the photostabilization of PVC films containing such compounds

Experimental

Irradiation Experiments

Photodegradation Measuring Methods

Results and Discussion

O ketone

Conclusion