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A polymer comprising recurring units of formula ( 4E) is decomposed under the action of acid to generate a hydroxyl group so that its solubility in various solvents may change. The acid labile group XE may be selected from a variety of 

such groups. Examples of the acid labile group XE are groups of formulae (Ll) to (L4), tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, andoxoalkyl groups of 4 to 20carbon atoms, like the acid labile group XA mentioned above. 

Illustrative examples of the recurring units having formula (4E) are given below, but not limited thereto. 

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