Random or block copolymers of a (meth)acrylic ester, which comprise structural units represented by general formulae (I) and (II) and have a number-average molecular weight of 1,000 to 50,000, a weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio, Mw/Mn, of 1.00 to 1.40, and a ratio of the repeating structural units represented by formula (I) to those represented by formula (II) of 1/9 to 9/1 (wherein R1 and R2 each independently represents hydrogen or methyl; R3 represents an optionally substituted C7-15 alicyclic group or an alkyl group having the alicyclic group; and R4 represents hydrogen, an optionally substituted C1-12 alkyl, optionally substituted C3-6 alicyclic or heterocyclic group, or substituted silyl group having a C1-8 alkyl and/or aryl group). The copolymers have each a unimodal narrow molecular weight distribution and an essential skeleton having at least one segment with a controlled structure comprising (meth)acrylic ester units each having an organic group containing a bulky alicyclic group.
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