Macromolecular Nomenclature Note No. 5

J. M. DeSimone* and W. V. Metanomski**
Nomenclature Committee
ACS Division of Polymer Chemistry, Inc.

In this fifth Macromolecular Nomenclature Note,(1) we have decided to highlight some of the key points associated with the naming(2) of block and graft copolymers to coincide with the symposium on "The Synthesis and Characterization of Block and Graft Copolymers" cosponsored by the Divisions of Polymer Chemistry and of Polymeric Materials: Science and Engineering.


BLOCK COPOLYMERS

Block copolymers are macromolecules which contain a linear arrangement of blocks or portions of a polymeric macromolecule that have at least one constitutional or configurational feature which is absent from the adjacent portions. For example, block copolymers made up of A and B structural units can have the following sequence arrangements

-AAAAAAAA-BBBBBBBB-
-AAAAAAAA-BBBBBBBB-AAAAAAAA-
-AABABAAABB-AAAAAAAA-BBBBBBBB-

where the sequences -AAAAAAAA-, -BBBBBBBB-, and -AABABAAABB- constitute blocks. The corresponding polymers are named

polyA-block-polyB
polyA-block-polyB-block-polyA
poly(A-stat-B)-block-polyA-block-polyB

A systematic source-based nomenclature for copolymers identifies the constituent monomers and provides a description of the sequence arrangement of the different types of monomeric units present. The structural diagrams, on the other hand, show the constitutional repeating units linked in a head-to-tail arrangement.(3)

Below are listed some examples of block copolymers taken from several papers in the symposium:

1. Polystyrene-block-poly(dimethyl-t-butylsilyl vinyl ether)

2. Poly(t-butyl methacrylate)-block-polybutadiene-block-poly(t-butyl methacrylate)

3. Poly[w-methoxyocta(oxyethylene) methacrylate]-block-poly(4-vinylpyridine)




GRAFT COPOLYMERS

Graft polymers are macromolecules that have blocks of one or more species connected to the main chain of a macromolecule as a side chain. These side chains have constitutional or configurational features that distinguish them from those in the main chain. In graft copolymers (as opposed to graft polymers) the distinguishing feature of the side chains is constitutional, i.e. the side chains are derived from at least one species of monomer that is different from the monomers which make up the main chain. For example, the arrangement

would be given the name

      polyA-graft-polyB

where the monomer named first (A) is that which makes up the backbone or main chain and the monomer named second (B) makes up the side chain. The designation (X) denotes a modified constitutional repeating unit of the main chain to which the side chain is attached or a junction unit usually derived from a macromonomer.

Below are some examples of graft copolymers taken from several different papers in the symposium:

1. Poly(ethyl acrylate)-graft-poly(vinylidene fluoride)

2. Poly(1,1-dihydroperfluorooctyl acrylate)-graft-poly(ethylene oxide)

This name reflects the polymeric chains only. The junction unit derived from a macromonomer, as shown on the structural diagram, can be named as a trivalent group: 1-(4-methylenephenyl)ethylene

3. Polypropylene-graft-poly(methyl methacrylate)

This name reflects the polymeric chains only. The junction unit derived from a macromonomer, as shown on the structural diagram, can be named as a trivalent group: 1,2,6-hexanetriyl





REFERENCES

1.Polym. Prepr. (Am.Chem.Soc., Div. Polym. Chem.) 1991, 32(1), 655-656; 32(3), 7-9; 1992, 33(2), 6-7; 1993, 34(1), 6-9.
2.IUPAC. "Compendium of Macromolecular Nomenclature" (The Purple Book). Metanomski, W. V. (ed.); Blackwell Scientific Publications, Oxford, 1991. Reviewed in Polym. Prepr. 1992, 33(1), 6-11.
3.IUPAC. "Graphic Representations of Macromolecules (Chemical Formulae for Polymers)". In preparation.


___________
*Department of Chemistry, CB #3290, Venable and Kenan Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, NC 27594-3290.

**Chemical Abstracts Service, P.O. Box 3012, Columbus, OH 43210.