Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
Lec-2
Basic Considerations :
Polymer is a substance composed of macromolecules, built by covalently joining at least 50 molecular mers, or the Constitutional
Repeating Units or CRU . The longest sequence of CRU defines the main chain of a macromolecule.
The main chain may be composed of a series of subchains, identified by some chemical of physical characteristic (e.g., tactic placement ).
The main chain may also contain long or short side chains or branches, attached to it at the branch points .
A small region in a macromolecule from which at least four chains emanate constitutes a crosslinking point.
A macromolecule that has only one crosslink is the star macromolecule .
A macromolecule consisting of several crosslinked chains, but having a finite molecular weight is a micronetwork.
A highly ramified macromolecule in which each CRU is connected to every other CRU is a polymer network . When the main chain of a macromolecule has numerous branch points from which linear side chains emanate, it is comb macromolecule .
The CRU is not necessarily identical to the source from which the macromolecule was prepared — it is the largest identifiable group in the polymer.

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
To discuss the structure of polymer molecules, one may consider the chemical nature of CRU, type of the linkages, the global macromolecular arrangement, and the topochemical character of the macromolecule, tacticity, etc. These are summarized in Table 1
Macromolecular compounds can be classified according to:
1. The chemical structure of the repeating unit (viz. polyamides,
polyesters, polyolefi ns).
2. The structure (viz. linear, branched, ladder, or crosslinked).
3. The phenomenological behavior or technological use.
4. The source of the compounds (viz., synthetic, natural, and derived
products).
Nomenclature Commission has published three sets of rules for naming polymers:
1. Traditional , trivial names are sanctioned by the historical use and
approved by IUPAC as an alternative (examples are listed in Table 2)
2. Structure-based nomenclature
3. Source based nomenclature proposed by the Commission.

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
Table 1: Macromolecular structures
Table 2: Traditional and systematic names of polymers

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
Structure-based nomenclature:
For organic, regular, single-strand polymers the structure-based system of naming polymers should be used. This nomenclature describes chemical structures rather than substances.
Three steps are to be followed in a sequence:
1. Identify the constitutional repeating unit, CRU.
2. Orient the CRU.
3. Name the CRU. The name of the polymer is poly(CRU).
The preferred CRU is one beginning with the subunit of highest seniority. The order of seniority is: heterocyclic rings, chains containing heteroatoms, (in the descending order O, S, Se, Te, N, P), carbocyclic rings, chains containing only carbon. The seniority is expressed by brackets and internal parentheses (see examples in Table 2).
After the CRU and its orientation, reading left to right , have been established, the CRU or its constituent subunits are named . The name (the largest identifiable unit) includes description of the main chain and the substituents. The subunits are named a ccording to the rules for nomenclature of organic chemistry . The name of the CRU is formed by citing, in order, the names of th e largest subunits within the CRU . More complicated, regular single-strand polymers can be represented as multiples of repeating units, such as [ABC]n. The name of the polymer is poly(ABC), where (ABC) stands for the names of A, B, and C, taken in the order of seniority.
Structure-based nomenclature is also applicable to copolymers having a regular structure, regardless of the starting materials used [viz. poly
(oxyethylene-oxyterephthaloyl)].
Source based nomenclature:
Different types of polymerization can take place with many monomers, and there are different ways for obtaining a polymer. Source based nomenclature is also the basis for naming and classifying copolymers .
When mers are not identical the polymerization leads to a copolymer.

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
For divalent mers a linear copolymer is obtained, but when at least some mers are able to join more than two units, the polymerization leads to
branched or crosslinked copolymer .
When the polymerization starts on a polymer chain of different chemical character that the one that is subsequently forming, the resulting structure is known as grafted copolymer .
Thus, the arrangement of the different types of monomeric units must be specified. Several types of arrangements are shown in Table 3, where A,
B, and C represent different CRU.
The systematic source-based nomenclature for copolymers involves identification of the constituent monomers, and description of their arrangement. This is achieved by citing the names of the constituent monomers after the prefix “poly”, and by placing between the names of each pair of monomers an italicized connective to denote the kind of arrangement by which those two types of monomeric units are related in the structure.

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
Table 3: Nomenclature of copolymers

Lec. 2: Polymer Structure & Nomenclature………….……Eng. Auda Jabbar Ms.C.
To describe polymers or polymer blends with greater precision the qualifiers listed in Table 4 have been suggested.
Table 4: Descriptors for non-linear macromolecules and macromolecular assemblies