Source-based Polymer Representations

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Source-based polymer representations enclose an entire discrete chemical substance in brackets. The mode of polymerization may be obvious from context, or it might be unknown. Source-based representations are useful when describing processes where the starting materials are known, but the exact structure of the reaction product is not.

You can create a source-based representation by enclosing a structure in "Monomer (mon)" brackets.

A source-based representation of poly(vinyl chloride) is shown below.

You can use "Mer (mer)" brackets for components of a copolymer where those individual components are known not to repeat themselves or alternate with the other components. An example is shown below.

Copolymers represent substances with more than one repeating unit. In general, you can use bracket type "Component (co)". You can also use "Copolymer, alternating (alt)", "Copolymer, random (ran)", and "Copolymer, block (blk)" to represent different specific types of copolymers in a source-based representation, but they are rarely used and their use is discouraged.

The bracket type, "Mixture, unordered (mix)" is not for polymers, but to represent a collection of substances that may all be present, but not necessarily in known amounts. Bracket type "Component (c)" indicates individual mixture elements.

An example is shown below.

Bracket type "Mixture, ordered (f)" is primarily used to describe manufacturing processes, where the ordering of components is a critical part of the process (and where a different ordering might produce a different final product. As with Unordered Mixtures, individual elements of an ordered mixture should be surrounded by brackets with a bracket usage of "Component (c)". Unlike with Unordered Mixtures, however, components of Ordered Mixtures must represent their ordering. You can do this by editing the "c" label with the text tool to include a number ("c1", "c2", and so on.)

You use the bracket type, "Multiple Group (#)" to indicate that the enclosed items are repeated a specific known number of times. Multiple Group brackets may enclose entire structures, or may enclose a portion of the structures only. You can edit the numeric repeat count with the text tool.

Examples follow.

Because Multiple Group brackets represent a specific repeat count (unlike the unknown repeat count of the other bracket types), it is possible to calculate accurate molecular weights (and related data) for such structures. That data is displayed in the Analysis window as with any other structure.

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