A monomer, diethyl alpha,alpha-dimethyl-m-isopropenylbenzyl carbamoylphosphonate, has been prepared by the base-catalyzed reaction of the isocyanate m-TMI (alpha,alpha-dimethyl-m-isopropenylbenzylisocyanate) with diethyl phosphite. The structure of the carbamoylphosphonate monomer and its styrene copolymer was confirmed spectroscopically, and the nature of the hydrogen bondings in the -NHC(=O)P(=O)(OR)(2) unit in the monomer and copolymer is discussed in detail. A bulk polymerization of the carbamoylphosphonate is very slow and tends to yield a crosslinked product, but a solution polymerization produced the soluble copolymers. The T-g(midpoint) of the homopolymer is low, 67 degrees C, and its capacity to complex UO2(NO3)(2) is very high, 28 wt % (19 mol %).