A method of making a polymer having the structure: wherein L is a linking group, R is a hydrocarbon group or a substituted-hydrocarbon group, and x is 2 or more, preferably from 2 to 100, more preferably from 2 to 50; and wherein each contains a plurality of polymer blocks, such that the moiety -L- has the structure {P n.....P 2 P 1}-L-{P 1 P 2.....P n} where each P n is an individual polymer block, the number of polymer blocks n in each being the same; wherein for each value of n the polymer blocks are identical; and wherein n is an integer of 2 or more, preferably from 2 to 100, more preferably from 2 to 50; the method comprising: (i) reacting, in the presence of a catalyst comprising a transition metal-ligand complex, a di-halo initiator of the structure halo-L-halo, where halo is Br, CI, or I, preferably Br, with a monomer of structure, or a mixture of two or more different monomers of structure: wherein R 1 or each R 1 is independently hydrogen or methyl; wherein X or each X is independently a hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, a substituted-hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, COOR 2, COSR 2, CONR 2 R 3, OCOR 2, CONHR 2, CN, COSiR 2 R 3 R 4 or Cl, wherein R 2, R 3 and R 4 are independently hydrogen, a hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, or a substituted-hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, to form a di-halo moiety with the structure halo-P 1 -L-P 1 -halo, where P 1 is a polymer block formed from at least 3 monomers of structure; (ii) repeating step (i), between 1 and n times, each time n, reacting, in the presence of a catalyst as described in step (i), the di-halo moiety formed in the previous step with a further monomer of structure and different from the monomer of structure used in the previous step, or a mixture of two or more different monomers of structure and different from the mixture of two or more different monomers of structure used in the previous step, to form a di-halo moiety with the structure halo- {P n.....P 2 P 1}-L-{P 1 P 2.....P n}-halo, where each P n is a polymer block formed from at least 3 monomers of structure, and n is an integer of 2 or more, preferably from 2 to 100, more preferably from 2 to 50; and (iii) reacting the di-halo moiety formed in step (i) or if step (ii) is used, the moiety formed in step (ii), with a dithiol compound of the structure HS-R-SH. (i) reacting, in the presence of a catalyst comprising a transition metal-ligand complex, a di-halo initiator of the structure halo-L-halo, where halo is Br, CI, or I, preferably Br, with a monomer of structure, or a mixture of two or more different monomers of structure: wherein R 1 or each R 1 is independently hydrogen or methyl; wherein X or each X is independently a hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, a substituted-hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, COOR 2, COSR 2, CONR 2 R 3, OCOR 2, CONHR 2, CN, COSiR 2 R 3 R 4 or Cl, wherein R 2, R 3 and R 4 are independently hydrogen, a hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, or a substituted-hydrocarbon group having from 1 to 50, preferably 1 to 30 carbon atoms, to form a di-halo moiety with the structure halo-P 1 -L-P 1 -halo, where P 1 is a polymer block formed from at least 3 monomers of structure; (ii) repeating step (i), between 1 and n times, each time n, reacting, in the presence of a catalyst as described in step (i), the di-halo moiety formed in the previous step with a further monomer of structure and different from the monomer of structure used in the previous step, or a mixture of two or more different monomers of structure and different from the mixture of two or more different monomers of structure used in the previous step, to form a di-halo moiety with the structure halo- {P n.....P 2 P 1}-L-{P 1 P 2.....P n}-halo, where each P n is a polymer block formed from at least 3 monomers of structure, and n is an integer of 2 or more, preferably from 2 to 100, more preferably from 2 to 50; and (iii) reacting the di-halo moiety formed in step (i) or if step (ii) is used, the moiety formed in step (ii), with a dithiol compound of the structure HS-R-SH.