丙烯酰胺-丙烯酸交联共聚凝胶结构与分子运动的~1H NMR自旋晶格弛豫研究

用1HNMR方法测定了交联度分别为10％,7.5％，5％，25％，1％，0．5％及0．25％的丙烯酰胺-丙烯酸与N，N’－亚甲基双丙烯酰胺交联共聚水凝胶中水及主链质子的化学位移谱及自旋晶格弛豫时间T1，并用BBP模型进行了讨论。结果表明，水和凝胶主链的质子线宽随交联度加大而明显增宽，只有在低交联度下，由空间立规度造成的精细分裂才能呈现出来；水凝胶体系中水自旋晶格弛豫时间T1随交联度加大而非单调地减小，寓示凝胶内部有较强的键合束缚水存在，并满足双相快交换模型。聚合物主链质子T1与水质子的T1弛豫行为相反，随交联度加大主链运动受限加强而使其运动减慢，反映了聚合物主链的大分子运动特征，发现主链（-CH-）与（－CH2－）质子T1之比可表征凝胶内部分子链运动的强弱；讨论了NMR弛豫与凝胶孔径结构的关联。

~1H NMR SPIN-LATTICE RELAXATION STUDIES ON THE STRUCTURE AND DYNAMICS OF AAm-AAc COPOLYMER HYDROGELS

NMR proton spin - lattice relaxation measurements in seven AAm - AAc copolymer hydrogels with different degrees of crosslinking were carried out, and the BBP theory was used to elucidate the dynamics of these copolymer gels. The T1 value of water is found to decrease with increasing the degree of crosslinking, and a maximum value of T1 can be found on the sample 5 which implies the existence of bound water that influence the relaxation behavior of bulk water. For the backbone protons, T1 is found to increase with increasing the degree of orosslinking. We also found that the ratio of relaxation time of the backbone CH to - CH2 - pro-tons can be used to characterize the dynamics of copolymer gels. The correlation between NMR relaxation time T1 and the mean pore radius of gels has been discussed .