Improved SSNMR Quantitative Methods And Their Application In Polymer Blends

As an essential fluoropolymer,Polytetrafluoroethylene(PTFE)is commonly mixed with 13C-1H engineering polymers to obtain favorable physical properties,such as high mechanical strength,excellent wear resistance and high chemical stability.It has been noted that,the relative content of PTFE determines the physical or electrochemical properties of PTFE contained materials.However,a proper way to quantify the component content of such PTFE mixture/blend or other 13C-1H/13C-19 F systems is still desired.In this work,a new cross depolarization pulse sequence,named r CDPz,was designed,aiming to measure the system with long T2I(such as PTFE)or under high MAS frequency condition.Combined with r CP sequence,we proposed two quatitative SSNMR methods,which has wide range of application and short-time comsumption.For most solid samples,DP consumes extraordinarily long time.In 2008,S.Zhang etc.[1]proposed QCP/QCPRC method which was access to provide quantitative information in notably short period of time.However,QCP/QCPRC is not applicable for systems with long T2 I or under high MAS rate experimental condition.To solve aforementioned problems,we designed r CDPz sequence and proposed r QCPz/r QCPzRC method.L-Alanine,L-Histidine,PTFE and L-Alanine/L-Histidine mixtures were used to evaluate the accuracy of r QCPz/r QCPzRC method.By comparing among three schemes of r CP,DP and r QCPz/r QCPzRC,it is demonstrated that r QCPz/r QCPzRC presents equal accuracy as DP experiment but consumes remarkably shorter experimental time.For 13C-1H/13C-19 F systems,a quantitative CP method named d QCPz/d QCPzRC is proposed,which aims to quantify the component content of 13C-1H/13C-19 F mixture or immiscible blend.Upon the tests of three samples of Alanine/PTFE mixture,Polystyrene/PTFE mixture and Poly(vinyl alcohol)/PTFE blend,the performances of three methods are compared,including d CP,DP and d QCPz/d QCPzRC.It is demonstrated that,d CP is not quantitative,whereas d QCPz/d QCPzRC provides an accuracy equivalent to the DP method.Moreover,d QCPz/d QCPzRC consumes notably shorter experimental time than that of DP.Those favorable performances imply that d QCPz/d QCPzRC method has potential to become a routine tool for measuring the component content of 13C-1H/13C-19 F systems for industrial or scientific research.