Modified freely jointed chain

This means that the polyethylene chain will be expanded significantly compared with a freely-jointed chain. The freely-jointed chain is assumed to be made up of a series of vectors with continually variable bond angles and no preferred conformations. For a real polymer chain this is not the case and allowance for this can be made by taking into account the effect of restricted rotation. This is due to the preference of the segments of the molecule to adopt low energy trans and gauche conformations. Equation (3.12) can be further modified to allow for this effect and becomes... 

Having obtained the average value of the square of the chain end-to-end distance and the distribution of end-to-end values about this mean, it is worth pausing and again asking if there is any relation between these results and results for real polymer molecules. In other words, how closely do freely jointed chains approximate actual macromolecules If the answer is not very closely, then how do we modify the freely jointed chain results to make them apply to polymers ... 

However, the freely jointed Kuhn chain is the most idealised model for a real macromolecule therefore, there exist several corrections taking into account specific features of the polymer structure. Thus, for chains in which LJA<10, condition (11.30) no longer holds. The modified condition is written as follows [94] ... 

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