ADAMANTANE AS A PROBE FOR STUDIES OF SPIN CLUSTERING WITH MULTIPLE-QUANTUM NMR

Time domain H-1 multiple quantum NMR (MQ NMR) was applied to study bin ary guest/host systems. We investigated protonated adamantane-h(16) (A -h(16)) molecules in deuterated crystalline adamantane-d(16) (A-d(16)) and in glassy polystyrene-d(8) (PS) for various guest concentrations and coupling times tau/tau(c). For pure A-h(16) crystals spin clusters of more than 1000 connected spins were observed. We observed the evol ution of the multiple quantum connectivities as a function of the coup ling time. In all cases the growth curves of the; multiple quantum ord ers can be described by a master curve, showing the validity of a scal ing law. For the diluted systems the master curve is obtained by multi plying the time axis with the square root of the dipolar line width (D elta nu)(1/2). The different local structure of the systems leads to c haracteristic growth curves, in particular to a quadratic function for the crystalline and to a linear function for the glassy material. For short coupling times these differences can be attributed to geometric al constraints caused by the polymer chains while for longer coupling times geometrical constraints and dynamics of the polymer chains can b oth be responsible for the different growth curves. The technique was applied to study slow phase separation processes in a solution of A-h( 16) in PS.