Definitions of Terms Relating to Crystalline Polymers (1988)

Preamble, preface 1. General definitions

2. Terminology relating to local conformation and structural aspects

3. Terminology relating to morphological aspects

4. Terminology relating to molecular conformation within polymer crystals

5. Terminology relating to crystallization kinetics

The recommendations embodied in this document are concerned with the terminology relating to the structure of crystalline polymers and the process of macromolecular crystallization. The document is limited to systems exhibiting crystallinity in the classical sense of three-dimensionally periodic regularity.

The recommendations deal primarily with crystal structures that are comprised of essentially rectilinear, parallel-packed polymer chains, and secondarily, with those comprised of so-called globular macromolecules. Since the latter are biological in nature, they are not covered in detail here. In general, macromolecular systems with mesophases are also omitted, but crystalline polymers with conformational disorder are included.

After a listing of some general definitions relating to crystalline polymers (Section 1), the subject is divided into sections dealing, successively, with local structural arrangements at the scale of a few bond lengths (Section 2), morphological aspects (Section 3), molecular conformation within polymer crystals (Section 4) and, finally, kinetic aspects of crystallization (Section 5). An alphabetical index of terms is provided for the convenience of the reader.

This document relies on the basic definitions of terms in polymer science. It is the second in a current series published by the Commission on Macromolecular Nomenclature dealing with definitions of physical and physicochemical terms in the polymer field (for the first, see Reference [2]).

1 GENERAL DEFINITIONS Term and Definition 1.1 crystallinity The presence of three-dimensional order on the level of atomic dimensions. Note Crystallinity may be detected by diffraction techniques, heat-of fusion measurements, etc. Some amount of disorder within the crystalline region is not incompatible with this concept.

1.2 crystalline polymer A polymer showing crystallinity. Notes 1. One- or two-dimensional order leads to mesophase structure. 2. The range of order may be as small as about 2 nm in one (or more) crystallographic direction(s) and is usually below 50 nm in at least one direction.

1.3 degree of crystallinity recommended symbols: wc for mass fraction; f c for volume fraction. The fractional amount of crystallinity in the polymer sample.

Notes

1. The assumption is made that the sample can be subdivided into a crystalline phase and an amorphous phase (the so-called two-phase model).

2. Both phases are assumed to have properties identical with those of their ideal states, with no influence of interfaces. 3. The degree of crystallinity may be expressed either as the mass fraction or as the volume fraction, the