Spin labels as the instrument for analysis of topochemistry of polymer-immobilized Ziegler catalytic systems

A spin labeling technique was used to investigate the topochemical characte ristics of polymer carriers and immobilized metal complexes. Functionalized polyethylenes (PE) such as PE-grafted-polyallylamine (1), PE-grafted-polyd iallylamine (2), and PE-grafred-poly-4-vinylpyridine (3); obtained by graft ing polymerization of the corresponding monomers, were used as polymer carr iers. Metal-containing polymers were obtained by immobilization to 2 with e ither TiCl4 (2/Ti) or Al(C2H5)(2)Cl (2/Al). The stable nitroxyl radical 2,2 ,6,6-tetramethyl-4-( 2'-oxy-4',6'-dichlorotriazine)piperidine-1-oxyl ((R)ov er dot(1)) was used for spin labeling 2 to give 2/(R)over dot(1), while 2,2 ,5,5,tetramethyl-3-(N-acetoamidiiodine)-pyrroilidine-1-oxyl ((R)over dot(2) ) was used for spin labeling 3 to give 3/(R)over dot(2). Radical 2,2,6,6-te lramethyl-4-hydroxy-pyperidine-1-oxyl ((R)over dot(3)) was bonded to 2/Ti a nd 2/Al to give 2/Ti/(R)over dot(3) and 2/Al/(R)over dot(3), respectively. The accessibility of the functionalized polymers 1-3 to interact with the s pin labels and the immobilized metal complexes was examined. Estimation of the effective distances between the spin labels and the dynamic behavior of nitroxyl radicals in the functionalized polymer matrixes and metal-contain ing polymers revealed several important features of spin-labeled systems. M etallation of a functional covering makes the polymer more accessible for s pin labeling and has a considerable effect on the dynamic characteristics o f polymer matrix. A change of the rotational activation energy of the spin labels from 15 kcal/mol in 2/(R)over dot(1) to 44 kcal/mol for 2/Ti(Al)/(R) over dot(3) in the temperature range 100-150 degreesC was observed.