Tetrazine mediated inverse Electron Demand Diels–Alder Reaction (IEDDA) is an important modification technique due to its high selectivity and super‐fast kinetics. Incorporation of tetrazine moieties on polymer chains requires multistep synthetic pathways and a post‐polymerization step leading to functional polymeric materials. Such approaches involve separate syntheses of polymer and the molecule which will be employed in modification. Herein, we introduce a straightforward synthetic approach for direct synthesis of tetrazine groups on polymers as side chains. As model systems, tetrazine functional poly(N‐isopropylacrylamide)‐and poly(ethylene glycol)‐based polymers from corresponding precursor polymers with nitrile moieties as pendant groups are prepared and IEDDA Click Reaction is achieved with trans‐cyclooctene derivatives. The click reaction is monitored by both NMR and UV–vis spectroscopies. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 673–680

Low-molecular-weight atactic poly(propylene oxide) and poly(epichlorohydrin) (PECH) were chlorinated on average up to 4.42 chlorine atoms per repeat unit. A study of the products showed that chlorine substitution preferentially occurred on already chlorinated repeat units, yielding chlorine -rich and chlorine -poor sequences. As the extent of chlorine substitution increased, the glass-transition temperature of the polymers markedly increased, and their solubility in most of the organic solvents drastically decreased. The chlorinated polymers were azidified with NaN 3 in dimethyl sulfoxide solutions. An analysis showed that azide groups replaced 99.8 -99.9% of the initially present chlorine atoms. As the azide content of the samples increased, initially opaque polymers become dark brown, and their solubility increased in water but decreased in organic solvents. Samples with approximately four or more azide groups per repeat unit were only soluble in dimethyl sulfoxide and water. The standard enthalpy of formation of the polymers became increasingly positive as the azide content increased. The enthalpy of formation of a sample with 4.42 N 3 /repeat unit was 6929 kJ/repeat unit, whereas this value was only 103 kJ/mol for classical GAP. An azidified sample from PECH (4.42 N 3 /repeat unit) was crosslinked with a commercial triisocyanide into a rubbery product. The density and ultimate tensile strength of the rubbery product were 1.44 g/cm 3 and 4.84 MPa, and it swelled about 10% at 20°C in water. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: [3785][3786][3787][3788][3789][3790] 2004 Key words: crosslinking; thermal properties; mechanical properties; calorimetry; NMR EXPERIMENTAL MaterialsAll solvents were purified by fractional distillation.Poly(propylene oxide) (PPO) was synthesized as described by Steiner et al. 1 The number-average molecular weight of PPO was 4000, which was calculated by end-group determination. Poly(epichlorohydrin) (PECH) was obtained from 3M Co.Chlorine gas was obtained from the oxidation of NaCl with KMnO 4 . The reaction flask was flushed with N 2 gas before the addition of concentrated H 2 SO 4 (ca. 40 wt %). Excess chlorine was absorbed in aqueous NaOH solutions. ProcedureThe chlorination of the polymers were achieved by the bubbling of Cl 2 gas into solutions of the polymers in carbon tetrachloride (2.5 wt %) at 60°C for several days. The rate of chlorination apparently increased with the intensity of sunlight, the partial pressure of Cl 2 , and the temperature. However, at temperatures higher than 60°C, because of the decrease in the solubility of Cl 2 , the rate of reaction slowed down. At the end of the chlorination, the solvent was distilled off, and the residue was extracted with benzene and neutralized with aqueous NaHCO 3 . Finally, the benzene solution was washed with distilled water and freezedried.The extent of chlorination was determined from both the stoichiometry of the reaction, through the measurement of the increase in the mass of the polymer, and the vo...