Acrylic star polymer

Abstract

An object of the present invention is to provide an acrylic acid-based star polymer which has a controlled structure with a narrow molecular weight distribution and acid decomposability. The star polymer contains, as a core portion, a polymer chain having a repeating unit derived from a polyacrylate which has at least two partial structures represented by formula (I): (wherein R 1 , represents a hydrogen atom or a methyl group, R 2 and R 3 each independently represents an organic group which is combined via a carbon atom, and a Cl carbon represents a carbon atom which is combined with a moiety via a carbon atom) and, as an arm portion, a polymer chain having a repeating unit derived from a (meth)acrylic ester represented by formula (II): (wherein R 4 represents a hydrogen atom or a methyl group, and represents an organic group), excluding a homopolymer chain having a repeating unit derived from a (meth)acrylic ester in which R 5 is a C1-C4 alkyl group when R 1 in formula (I) is a methyl group.

1 . A star polymer characterized by comprising, as a core portion, a polymer chain having a repeating unit derived from a polyacrylate which has at least two partial structures represented by formula (I): 
     
       
         
         
             
             
         
       
     
     (wherein R 1  represents a hydrogen atom or a methyl group, R 2  and R 3  each independently represents an organic group which is combined via a carbon atom, and a Cl carbon represents a carbon atom which is combined with a moiety via a carbon atom) and, as an arm portion, a polymer chain having a repeating unit derived from a (meth)acrylic ester represented by formula (II): 
     
       
         
         
             
             
         
       
     
     (wherein R 4  represents a hydrogen atom or a methyl group, and represents an organic group), excluding a homopolymer chain having a repeating unit derived from a (meth)acrylic ester in which R 5  is a C1-C4 alkyl group when R 1  in the formula (I) is a methyl group. 
   
   
       2 . The star polymer according to  claim 1 , characterized in that the polyacrylate which has at least two partial structures represented by formula (I) is a diacrylate represented by formula (III): 
     
       
         
         
             
             
         
       
     
     (wherein R 11  and R 21  each independently represents a hydrogen atom or a methyl group, R 12 , R 13 , R 22  and R 23  each independently represents an organic group which is combined via a carbon atom, and R 33  represents a divalent linking group). 
   
   
       3 . The star polymer according to  claim 2 , characterized in that R 33  is an unsubstituted or substituted alkylene group in formula (III). 
   
   
       4 . A star polymer characterized by comprising an arm portion having at least one repeating unit selected from the group consisting of a repeating unit having a lactone ring and a repeating unit having an alicyclic skeleton. 
   
   
       5 . The star polymer according to  claim 4 , characterized by comprising a core portion having a repeating unit derived from a polyacrylate having at least two partial structures represented by formula (I): 
     
       
         
         
             
             
         
       
     
     (wherein R 1  represents a hydrogen atom or a methyl group, R 2  and R 3  each independently represents an organic group which is combined via a carbon atom, and a Cl carbon represents a carbon atom which is combined with a moiety via a carbon atom).