Preparation Of Phenolic Films Mediated By High Frequency Ultrasound

Sonochemistry is a technical method that applies the physical and chemical effects induced by ultrasound into chemical reactions.Due to the unique physical and chemical phenomenon caused by ultrasonic cavitation,sonochemistry has been widely used in the fields of micro/nanomaterial preparation,emulsion preparation,polymer synthesis,biomedicine,food processing and environmental remediation in recent years.Based on the frequency,ultrasound includes low and high frequency ultrasound.In the process of the high frequency ultrasound,a large number of free radicals are formed in the liquid medium,which trigger various chemical reactions.In order to enrich the application field of high frequency ultrasound,we explore the fabrication of functional films using high frequency ultrasound.In this thesis,a series of phenolic films composed of different molecules are prepared by high frequency ultrasound.Furthermore,we discuss the critical role of high frequency ultrasound,as well as the formation mechanism and function of the films.This thesis includes the following three chapters.Chapter ? focuses on the introduction of sonochemistry and the concept of high frequency ultrasound,the mechanism of acoustic cavitation effect,and the application of sonochemistry in the fields of material synthesis,environmental engineering,food engineering,etc.Both of the properties and applications of polyphenol compounds and phenolic films are summarized.In chapter ?,we report the polymerization of dopamine in alkaline,neutral,acidic and oxygen-free environments as well as the preparation of polydopamine(PDA)films on various substrates using high frequency ultrasound.The results from the contact angle and atomic force microscopy measurements show that PDA films can be formed on various substrates under acidic and oxygen-free conditions by high frequency ultrasound,which breaks through the dependence on pH and dissolved oxygen in traditional polymerization of dopamine.ON-OFF experiments indicate that the oxidative free radicals produced by ultrasonic cavitation play an important role in the polymerization of dopamine.In chapter ?,we report thin films obtained from phenol and phenyl derivatives through high frequency ultrasound combined with Fenton(Sono-Fenton)reaction.The UV-vis absorption spectra and mass spectrometry show that the monomer undergoes oxidative polymerization to form derivatives with catechol structures,which can coordinate with metal ions to form films.The phenolic films can be formed on various substrate materials.This strategy overcomes the dependence on catechol groups of traditional methods in preparation of metal-phenolic films,thereby introducing more functional aromatic molecules into films.