A series of ethylene-acrylic acid copolymers either isothermally crystallized or melt-quenched were studied by 13C CP／MAS and variable-temperature 1H wide-line NMR spectroscopy

with the emphasis on the mobility of the noncrystalline region．It is found that with the increase of the comonomer (acrylic acid) content

the chain mobility of the noncrystalline region decreases

while the content of the noncrystalline ethylene segments increases．Such an extraordinary observation can be explained by the fact that the hydrogen bonds formed between the carboxyl groups in the noncrystalline region increases with increasing the acrylic acid content．An indirect measurement of 1H spin-spin relaxation time by employing a modified 13C CP／MAS pulse sequence suggests that the mobility of the noncrystalline ethylene segments is greatly restricted by the hydrogen bonding interactions．