In the "Macromolecular Nomenclature Notes" published in the previous issues of Polymer Preprints,(1) we reported progressively on the recommendations of the Commission on Macromolecular Nomenclature of the International Union of Pure and Applied Chemistry (IUPAC), ranging from source-based nomenclature for homopolymers and copolymers to structure-based nomenclature for regular and irregular single-strand and double strand polymers. We also published a number of nomenclature notes as "The Back Page" in Polymeric Materials: Science and Engineering (PMSE Proceedings).(2)

The source-based nomenclature has now been extended for non-linear macromolecules and macromolecular assemblies.(3) The non-linear macromolecules comprise branched, graft, comb, star, cyclic and network macromolecules. The macromolecular assemblies comprise polymer blends, interpenetrating polymer networks, and polymer-polymer complexes.

It is of interest to note that the proposal for naming such non-linear macromolecules and assemblies was submitted to this Nomenclature Committee by one of the authors (LHS) many years ago. In the interest of international cooperation and standardization of macromolecular nomenclature, it was decided to submit the proposal to the IUPAC Commission. As it might have been expected, the Commission members contributed many additional ideas. The author of the original proposal became a member of the IUPAC Working Party, contributed to the subsequent drafts of the recommendations, and is a coauthor of the final published version. A few of these ideas, now published, remain controversial.

Even when a compromise has been reached on these controversial subjects, not every one is happy. There remains a difference of opinion with respect to, for instance, the definition of crosslink. The recently published IUPAC "Glossary of Basic Terms in Polymer Science"(4) defines it as "a small region in a macromolecule from which at least four chains emanate", while others think that three chains emanating from a site constitute a crosslink. Glycerol, for instance, is a common crosslinking trifunctional monomer,(5) which is called a branch point in two of the references.(3,4)

Most points, however, are agreed on and are important for more clearly discussing polymer structure. Here are some extracts from the recommendations.

The following italicized qualifiers can be used as both prefixes (e.g., blend-, net-) and infixes (connectives) (e.g., -blend-, -net-) to designate the skeletal structure of non-linear macromolecules or macromolecular assemblies:

cyclic: cyclo
branched, unspecified: branch
short-chain-branched: sh-branch
long-chain-branched: l-branch
branched with branch point of functionality f: f-branch
comb: comb
star: star
star with f arms: f-star
network: network
crosslink: i (Greek iota)
polymer blend: blend
interpenetrating polymer network: ipn
semi-interpenetrating polymer network: sipn
polymer-polymer complex: compl

In naming non-linear homopolymer molecules, the italicized prefix for the skeletal structure of the macromolecule is placed before the source-based name of the constituent linear chain.

Assemblies of macromolecules held together by non-covalent bonds are named by a combination of the names of the constituent macromolecules with an italicized connective between them.

Comb macromolecule is a macromolecule comprising a main chain with multiple trifunctional branch points from each of which a linear side-chain emanates.

Examples:

polystyrene-comb-polyacrylonitrile
(equivalent to polystyrene-graft-polyacrylonitrile)

comb-poly(styrene-stat-acrylonitrile)
(both the main chain and side chains are statistical copolymer chains of styrene and acrylonitrile)

polystyrene-comb-[polyacrylonitrile; poly(methyl methacrylate)]
(polystyrene with polyacrylonitrile and poly(methyl methacrylate) side chains)

Star macromolecule is a macromolecule containing a single branch point from which linear chains (arms) emanate.

Examples:

4-star-polystyrene
(a four-armed star of polystyrene)

star-(polyA-block-polyB-block-polyC)
(star copolymer molecule, each arm of which consists of the same block-copolymer chain)

star-(polyA; polyB; polyC)
(a variegated star copolymer molecule consisting of arms of polyA, arms of polyB, and arms of polyC)

star-(polyacrylonitrile; polystyrene) (M_r 100,000:20,000)
(star macromolecule consisting of arms of polyacrylonitrile of a total M_r (relative molecular mass) = 100,000 and arms of polystyrene of a total M_r = 20,000)

Network is a highly ramified macromolecule in which essentially all constitutional units are connected to all other constitutional units and to the macroscopic phase boundary by many permanent paths through the macromolecule. In a covalent network all the permanent paths are formed by covalent bonds. In a physical network, some of the bonds are formed by physical interactions. A micronetwork contains cyclic structures and of colloidal dimensions.

Examples:

net-polystyrene-i-divinylbenzene
(polystyrene crosslinked with divinylbenzene to form a network)

net-poly[styrene-alt-(maleic anhydride)]-i-(ethylene glycol)
(alternating copolymer of styrene and maleic anhydride crosslinked with ethylene glycol to form a network)

Polymer blend is a macroscopically homogeneous mixture of two or more different species of polymer. The general use of the term "polymer alloy" is discouraged. [This discouragement is also not unanimous, especially when used in the sense of having "modified" interfaces.6]

Examples:

polystyrene-blend-poly(2,6-dimethylphenol)

poly(methyl methacrylate)-blend-poly(n-butyl acrylate)

Semi-interpenetrating polymer network (SIPN) is a polymer comprising one or more networks and one or more linear or branched polymers characterized by the penetration on a molecular scale of at least one of the networks by at least some of the linear or branched macromolecules.

Example:

(net-polystyrene)-sipn-poly(vinyl chloride)
(SIPN of a polystyrene network and a linear poly(vinyl chloride)

Interpenetrating polymer network (IPN) is a polymer comprising two or more networks which are at least partially interlaced on a molecular scale but are not covalently bonded to each other and cannot be separated unless chemical bonds are broken.

Example:

[net-poly(styrene-stat-butadiene)]-ipn-[net-poly(ethyl acrylate)]
(IPN of two networks)

Researchers in the field of multicomponent polymer materials are urged to look up (Ref. 3), as this abstract cannot do justice to the full document.

REFERENCES

1.Polym. Prepr. 1991, 32(1), 655-656; 1992, 33(2), 6-7; 1993, 34(1), 6-9; 1994, 35(1), 6-9; 1995, 36(1), 6-9; 36(2), 6-9; 1996, 37(1), 6-9.
2.Polym. Mater. Sci. Eng. 1993, 68, 341; 69, 575; 1995, 72, 612-613; 1996, 74, 445; see also Spring and Fall 1998 issues.
3.IUPAC. "Source-Based Nomenclature for Non-Linear Macromolecules and Macromolecular Assemblies". Pure Appl. Chem. 1997, 69 (December).
4.IUPAC. "Glossary of Basic Terms in Polymer Science". Pure Appl. Chem. 1996, 68, 2287-2311.
5.Elias, H. G. "An Introduction to Polymer Science". VCH, Weinheim, 1997, p. 165; and other books.
6.Utracki, L. A. "Polymer Alloys and Blends: Thermodynamics and Rheology". Hanser, Munich, 1990.


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^aDepartments of Chemical Engineering and Materials Science and Engineering, Materials Research Center,
Center for Polymer Science and Engineering, and Polymer Interfaces Center, Lehigh University, 5 East
Packer Ave, Bethlehem, PA 18015-3194.

^bChemical Abstracts Service, P.O. Box 3012, Columbus, Ohio 43210-0012.