Norbornene–ethylene copolymers were prepared using the metallocene catalyst ethylene bis (indenyl) zirconium dichloride with MAO, and their microstructure was characterized with 1H‐NMR and 13C‐NMR methods. From a Cosy 1H‐NMR spectrum it was found that all norbornene units are enchained in the exo‐configuration. The sequence distribution of norbornene units was investigated using 13C‐1H correlations, hmqc for one‐bond correlations, and hmbc for two‐ or three‐bond correlations. It was shown that norbornene diads were formed at a high norbornene content (45 mol %). When further increasing the norbornene incorporation (66 mol %) a number of new signals were obtained. A Cosy 1H‐NMR spectrum revealed a new crosspeak which, according to the corresponding 13C‐NMR shifts (hmqc), correlated well with a terminal unit of a trimer of norbornene. This means that at very high norbornene contents, norbornene triads can be formed. Because the formation of isotactic norbornene triads is very difficult to understand from a sterical point of view, an epimerization process causing stereoirregularities in the norbornene triad is proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1633–1638, 1998

The free radical copolymerization and multipolymerization of olefins with acrylic monomers in the presence of acids has been studied. It was found that Bronsted acids are as suitable complexing agents for the acrylic comonomer as the up to now exclusively used Lewis acids.The effectiveness of the Bronsted acids, e.g. carboxylic acids, for obtaining alternating copolymers increased with the pKs value, and trifluoroacetic acid turned out to be the acid of choice. The variation of the Lewis acid-type complexation agents was extended by the zinc chloride diethylether complex which is advantageous over ZnCI, or other Lewis acids because of its good solubility and recycling practicability, which is also a feature of the Bronsted acids.The versatility of the new complexing agent systems was demonstrated in a series of co-and multipolymerizations, and ethyl cyanoacrylate was employed for the first time as electron acceptor comonomer. The properties of the copolymers with periodic comonomer sequences varied systematically with their composition, e.g. the glass transition temperature and the degree of crystallinity.

The free radical copolymerization of ethene and ethyl cyanoacrylate (ECA) in the presence of Lewis and Brensted acids has been studied in detail. Both trifluoroacetic acid (TFA) and ZnClz.Et,O were found to be useful complexing agents for synthesizing highly alternating copolymers of olefins and ECA. The influence of the complexing agents was quantified by determination of the copolymerization parameters r, of ECA for ECA/ET copolymerization. The synthesized copolymers showed unusual thermal behavior with regard to their alternating structure. This was established by the semi-crystallinity and the variation of the glass transition temperature with the degree of alternation.

The free radical copolymerization of ethene (ET) with acrylonitrile (AN) in the presence of carboxylic acids has been studied. Carboxylic acids and trifluoroacetic acid (TFA) in particular were found to be useful complexing agents for acrylonitrile with regard to the alternating copolymerization with ethene. The complexation via hydrogen bonding could be observed by IR analysis of the stretching frequency of the nitrile group in the monomer. The complex formation resulted in a decrease of the copolymerization parameter r 1 of the complexed and the uncomplexed comonomer acrylonitrile, which was found to decrease with increasing TFA/AN ratio. The degree of alternation could be increased by increasing the TFA/AN or the ET/AN ratio in the initial polymerization mixture. Almost strictly alternating copolymers were obtained with TFA as solvent. The copolymers showed high crystallinity and melting temperatures similar to the strictly alternating copolymer, which has been synthesized in the presence of EtAlCl2 as a Lewis acid.