Design And Application Study Of High-Efficiency SSNMR Quantitative Methods

Solid-state nuclear magnetic resonance(SSNMR)has become an effective technique for the investigation of structure and dynamics.As a tool of dynamics study,spin-lattice relaxation time(T1)plays a significant role in understanding the structure and motions,especially for polymers.With the aid of T1 data,plenty works have been devoted gaining the information of polymer crystallinity,lamellar thickness,local chain dynamics,as well as the structure of branch chains.Apparently,fast and precise technique for T1 measurement is the prerequisite issue of aforementioned aspects.In the case of 13C T1 measurement,inversion recovery(IR)method is more suitable for the mobile systems with short 13C T1 values.Torchia method is mainly employed in measuring 13C T1 for the rigid systems with strong heteronuclear dipole coupling.However,for the systems containing domains with marked different local mobility or proton distribution,neither IR nor Torchia is suitable.Apart from the dynamics investigation,the SSNMR techniques for structure research also attracts much interest.Especially,several efficient and accurate quantitative methods have been successively proposed by SSNMR researchers for gaining various quantitative information.However,most of those methods are applicable in limit types of systems.In this work,we proposed two SSNMR quantitative methods for the dynamics and structure investigation,respectively.The relating overview is as follows:1.IR and Torchia methods are commonly used for determining SSNMR 13C T1 values.However,for the systems containing domains with marked different local mobility or proton distribution,neither IR nor Torchia is suitable.In this work,we propose a new method,named DP-Torchia,for the measurement of 13C T1.Apart from the common samples that are suitable either for IR or for Torchia scheme,DP-Torchia is also designed for the materials containing domains with marked different local mobility or sharply distinct proton distribution.Based on the testing on L-alanine/adamantane(Ala/Ada)mixture as well as the polymer blend of polyvinyl alcohol and polytetrafluoroethylene(PVA/PTFE),it is demonstrated that the accuracy of DP-Torchia results are in accordance with those obtained from IR and Torchia.Moreover,DP-Torchia consumes shorter experimental time with less work of data processing.Further works will be devoted on the method applications on more polymer systems,such as semi-crystalline polymers or bulk heterojunctions.2.Multiple-CP quantitative technology has potential application in the analysis of molecular structure,group ratio,blending components and phase composition.However,the accuracy of Multiple-CP method is sensitive to the system properties and the experimental conditions.Especially,the T1?H(spin-lattice relaxation time in a rotating coordinate system of 1H)effect induces the loss of the 13C magnetization built up via 1H?13C polarization,which largely affect the accuracy of the measured results.To eliminate the effect of T1?H,an improved Multiple-CP pulse sequence,named as MultiCP-LGCP,is designed and evaluated.According to the testing results of two model samples,it is revealed that the MultiCP-LGCP method reduces to the impact of T1?H relaxation and improves the tolerance of the system parameter T1?H and experimental parameter tP.Further works will focus on the quantification investigation on rigid mixtures and multi-crystalline systems.