to polymerization, and the polymerization be followed by  deprotection with weak acid and water. Alternatively, the  hydroxy group may be replaced by an acetyl, formyl, pivaloyl  or similar group prior to polymerization, and the polymeriza- tion be followed by alkaline hydrolysis.  In a more preferred embodiment, the polymer serving as  base resin has further copolymerized therein recurring units  ( d) selected from units ( dl) to ( d5) ofindene, acenaphthylene,  chromone, coumarin, and norbornadiene, or derivatives  thereof, represented by the following formula (6).  76  US 9,152,050 B2  75  X  00  ~  /,  R2s  ~o  (I}-/  R2s  (6)  0  Herein R$^{25 }$is each independently hydrogen, a C$_{1}$-C$_{30 }$alkyl,  haloalkyl, alkoxy, alkanoyl or alkoxycarbonyl group, C$_{6}$-C$_{10 }$ aryl group, halogen, or 1,1,1,3,3,3-hexafluoro-2-propanol  group, and W $^{6 }$is methylene, oxygen or sulfur. As used herein,  the term "haloalkyl" refers to alkyl in which some or all  hydrogen atoms are substituted by halogen.  Examples of suitable monomers from which recurring  units ( dl) to ( d5) of indene, acenaphthylene, chromone, cou› marin, and norbomadiene derivatives are derived are given  below.  In the case of a monomer having a hydroxyl group, the  hydroxyl group may be replaced by an acetal group suscep› tible to deprotection with acid, typically ethoxyethoxy, prior 