A Brønsted-Lowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium:

##STR00001## where: M is tantalum (Ta), vanadium (V) or niobium (Ni); R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are independently H, F, Cl, Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring are taken together to form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

A BrnstedLowry acid initiator system for cationic polymerization of an ethylenically unsaturated monomer involves an initiator having a structure of Formula (I) in an anhydrous polymerization medium (I) where: M is tantalum (Ta), vanadium (V) or niobium (Ni); each R.sub.1 is independently H, OR.sub.6, F, Cl, Br, I or alkyl, where R.sub.6 is H or alkyl; R.sub.2, R.sub.3, R.sub.4 and R.sub.5 are independently H, F, Cl Br, I, alkyl or aryl, or two or more of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on a same benzene ring form a bicyclic, tricyclic or tetracyclic moiety with the benzene ring, with the proviso that all of R.sub.2, R.sub.3, R.sub.4 and R.sub.5 on the same benzene ring are not H; L is absent or a molecule that coordinates to H.sup.+; and, x is 0 when L is absent, or x is 0.5 or more when L is present.

##STR00001##

A method of polymerizing a first, and a second class of monomers to form product polymer. The first class of monomers polymerize via a radical pathway in the presence of light, and the second class of monomers polymerize via an insertion pathway in the absence of light.

[Problem] Provided is a cell-adhesive composition including an oxyethylene chain-containing polymer having excellent biocompatibility and excellent reactivity.

[Solution]A cell-adhesive composition according to the present invention includes an oxyethylene chain-containing polymer represented by the following general formula (1):

##STR00001##

(wherein, in the general formula (1), R.sup.1 is (CH.sub.2).sub.pSH, (CH.sub.2).sub.pN.sub.3, (CH.sub.2).sub.pNH.sub.2, or (CH.sub.2).sub.pCOOH, and p is an integer of 1 to 5; R.sup.2 to R.sup.4 are each independently hydrogen or a C.sub.1-10 alkyl group; R.sup.5 is a C.sub.1-10 alkyl group; R.sup.6 is hydrogen or a C.sub.1-5 alkyl group; R.sup.7 is a C.sub.1-10 alkyl group; n is an integer of 5 to 1000; m is an integer of 1 to 10; and q is an integer of 0 to 5).

[Problem] Provided is an oxyethylene chain-containing polymer having excellent biocompatibility and still having excellent reactivity.

[Solution] An oxyethylene chain-containing polymer according to the present invention is represented by the following general formula (1):

##STR00001##

(wherein, in the general formula (1), R.sup.1 is (CH.sub.2).sub.pSH, (CH.sub.2).sub.pN.sub.3, (CH.sub.2).sub.pNH.sub.2, or (CH.sub.2).sub.pCOOH, and p is an integer of 1 to 5; R.sup.2 to R.sup.4 are each independently hydrogen or a C.sub.1-10 alkyl group; R.sup.5 is a C.sub.1-10 alkyl group; R.sup.6 is hydrogen or a C.sub.1-5 alkyl group; R.sup.7 is a C.sub.1-10 alkyl group; n is an integer of 5 to 1000; m is an integer of 1 to 10; and q is an integer of 0 to 5).