The synthesis of the easily decomposable ionic monomer 2-tert-butoxy-N-[2-(methacryloyl-oxy)ethyl]-N,N-dimethyl-2-oxoethanammonium chloride (3) via thermally induced syn-elimination of a tert-butyl ester group was realized simply by mixing N,N-dimethylaminoethyl methacrylate (1) and tert-butyl chloroacetate (2) at ambient temperature without solvent. The obtained salt was polymerized via free radical polymerization. The decomposition and foaming via iso-butene formation takes place by heating up to about 160 °C. IR, DSC, TGA, and GC/MS measurements were performed to follow this pyrolysis reaction. Furthermore, the copolymerization of 3 with N-isopropylacrylamid (NiPAAm, 5) was carried out with different monomer ratios. Molar mass distributions were measured using an asymmetrical flow field-flow fractionation (aFFFF) system. The obtained copolymers 6–10 exhibit lower critical solution temperature (LCST) behaviour in water with cloud points at different temperatures depending on the monomer ratio.