Investigation On The Mechanism Of Diffusion Behavior/Chemical Reaction In The Polymer System By Infrared Spectroscopy

Fourier transform infrared spectroscopy(FTIR)is an effective method to track the diffusion behavior/chemical reaction process in the polymer system and to monitor the changes of molecular interactions and structures in the process at the molecular level.Two-dimensional correlation spectroscopy(2Dcos),as an analysis method,can greatly improve the resolution of the original spectrogram and identify the response sequence of groups along with perturbation direction.Our work will monitor the diffusion behavior/chemical reaction process using FTIR,and explore the transformation of molecular interactions and mechanisms at the molecular level in the meantime.This work can be divided into 5 chapters,and 3 specific systems are involved:The first chapter is the overall introduction of characterization method Fourier transform infrared spectroscopy(FTIR)and analysis method Two-dimensional correlation spectroscopy(2Dcos)used in the study.It simply introduces the FTIR and 2Dcos,mainly explains the spectrum reading rules of 2Dcos.Finally,perturbation correlation moving window(PCMW)technique derived from 2Dcos are introduced.In chapter two,the diffusion behavior is investigated in a typical gel polymer electrolyte system,where the electrolytic salt is Lithium bis(trifluoromethylsulfonyl)imide(Li TFSI),the solvent is propylene carbonate(PC)and the host polymer is poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF-HFP)).The diffusion behavior of the PC-Li TFSI electrolyte in the P(VDF-HFP)film is monitored in-situ by the time resolved Attenuated total reflectance-Fourier transform infrared(ATR-FTIR)spectroscopy at different temperatures(25 ?,35 ?,45 ?,55 ?),which can simultaneously provide information on the diffusion coefficients and molecular interactions within the diffusion system through the qualitative and quantitative analysis.It is proposed that the results herein would provide a molecular mechanism of the dynamic diffusion behavior of PC-Li TFSI electrolyte in P(VDF-HFP).In chapter three,the diffusion process of BTCA aqueous solution in the viscose film was monitored in-situ by the time resolved ATR-FTIR spectroscopy at different temperatures(30 ?,40 ?,50 ?,60 ?).Combining ATR-FTIR and 2Dcos analysis technology,it shows that the diffusion coefficient D increases with the increase of temperature from the molecular level,and the solvent water molecules in the multi-component system diffuse into the viscose fiber before BTCA.In chapter four,the heat-induced esterification reaction between silk and 1,2,3,4-butanetetracarboxylic acid(BTCA)under the catalyzing of sodium hypophosphite(SHP)is investigated by means of FTIR spectroscopy in combination with PCMW technique and 2Dcos.It mainly explores the change of molecular interaction and chemical transformation in the whole reaction process,and further explores the reaction mechanism from the microscopic molecular level.Two main stages could be identified in the heating process from 30 to 190 ? for the reaction system: the formation of cyclic anhydride and the esterification.In chapter five,the application of FTIR combined with 2Dcos in polymer systems is summarized.Our work uses FTIR to monitor the diffusion behavior/chemical reaction process in-situ.Combining PCMW and 2Dcos analysis,it explores the transformation of molecular interaction and chemical structure from the molecular level,and analyzes the mechanism of the diffusion/chemical reaction process.