A method of preparing a polyisobutylene oligomer or polymer in a one step reaction, comprising reacting components as shown below: where: R 1 is an initiator core structure independently selected from alkyl, heteroalkyl, aryl, heteroaryl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl and alkoxy; X is an initiating site bonded to the initiator core structure independently selected from halide, alkoxy, ester; m is an integer from 2 to 1,000; n is an integer from 1 to 20; and, CAP is a capping reagent selected from one or more of following structures 1 to 3; 1. Ar-(EDG-R 2 -Y) q 2. (Ar) p -Ar-(EDG-R 2 -Y) q 3. PAH-(EDG-R 2 -Y) q where EDG is an electron donating group selected from O, NR 3, S, R 4; R 2 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; R 3 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; R 4 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; p is an integer from 1 to 20; q is an integer from 1 to 20; Y can be independently selected from (meth)acrylate, OH, epoxy, oxetane, cyanate, isocyanate, urethane, urea, NR 5 R 6, SR 7, Si(OR 8) i R 9 3-i, where R 5, R 6, R 7, R 8, R 9 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl and i = 0-3; and wherein the ratio of the capping reagent to polymer end-chain, calculated as ratio = equivalents of the capping or functionalization reagent / equivalents of polymer end-chain, is in the range of 0.7 to 2. R 1 is an initiator core structure independently selected from alkyl, heteroalkyl, aryl, heteroaryl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl and alkoxy; X is an initiating site bonded to the initiator core structure independently selected from halide, alkoxy, ester; m is an integer from 2 to 1,000; n is an integer from 1 to 20; and, CAP is a capping reagent selected from one or more of following structures 1 to 3; 1. Ar-(EDG-R 2 -Y) q 2. (Ar) p -Ar-(EDG-R 2 -Y) q 3. PAH-(EDG-R 2 -Y) q 1. Ar-(EDG-R 2 -Y) q 2. (Ar) p -Ar-(EDG-R 2 -Y) q 3. PAH-(EDG-R 2 -Y) q where EDG is an electron donating group selected from O, NR 3, S, R 4; R 2 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; R 3 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; R 4 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl; p is an integer from 1 to 20; q is an integer from 1 to 20; Y can be independently selected from (meth)acrylate, OH, epoxy, oxetane, cyanate, isocyanate, urethane, urea, NR 5 R 6, SR 7, Si(OR 8) i R 9 3-i, where R 5, R 6, R 7, R 8, R 9 can be independently selected from H, alkyl, heteroalkyl, alkenyl, heteroalkenyl, alkynyl, heteroalkynyl, aryl, heteroaryl and i = 0-3; and wherein the ratio of the capping reagent to polymer end-chain, calculated as ratio = equivalents of the capping or functionalization reagent / equivalents of polymer end-chain, is in the range of 0.7 to 2.