A compound having a group represented by the formula (Ia): ##STR00001##
wherein R.sup.1 represents a C.sub.1 to C.sub.8 fluorinated alkyl group, R.sup.2 represents a group having an optionally substituted C.sub.5 to C.sub.18 alicyclic hydrocarbon group, and * represents a binding site.

Particles of a fluorine-containing polymer used as a transparent solid material in an artificial transparent frozen soil is provided. The fluorine-containing polymer is poly[4,5-difluoro-2,2bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene], with a refractive index of 1.31 and a density of 2.1-2.3 g/cm.sup.3. The particles have a particle diameter of 0.25-2.0 mm or a particle diameter 0.074 mm, and have irregular shapes. When particles of the fluorine-containing polymer are used as a transparent solid material for preparing a transparent frozen soil, the prepared transparent frozen soil has high transparency, low price, no toxicity and no harm, good similarity with the properties of a natural frozen soil body, can substitute natural frozen soil, is used for simulating complicated geological conditions, and is effectively used in model tests in geotechnical engineering.

Particles of a fluorine-containing polymer used as a transparent solid material in an artificial transparent frozen soil is provided. The fluorine-containing polymer is poly[4,5-difluoro-2,2bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene], with a refractive index of 1.31 and a density of 2.1-2.3 g/cm.sup.3. The particles have a particle diameter of 0.25-2.0 mm or a particle diameter 0.074 mm, and have irregular shapes. When particles of the fluorine-containing polymer are used as a transparent solid material for preparing a transparent frozen soil, the prepared transparent frozen soil has high transparency, low price, no toxicity and no harm, good similarity with the properties of a natural frozen soil body, can substitute natural frozen soil, is used for simulating complicated geological conditions, and is effectively used in model tests in geotechnical engineering.

A resist composition which includes a polymer compound including a structural unit which is derived from an acrylic ester in which the hydrogen atom bonded to an α-position carbon atom may be substituted with a substituent and which has a lactone-containing cyclic group containing other electron withdrawing groups such as a cyano group at a side chain terminal, and a compound whose a conjugate acid has an acid dissociation constant (pKa) of less than 3.

A monomer has the structure

##STR00001##

wherein R is an organic group comprising a polymerizable carbon-carbon double bond or carbon-carbon triple bond; X and Y are independently at each occurrence hydrogen or a non-hydrogen substituent; EWG1 and EWG2 are independently at each occurrence an electron-withdrawing group; p is 0, 1, 2, 3, or 4; n is 1, 2, 3, or 4; and M.sup.+ is an organic cation. A polymer prepared from monomer is useful as a component of a photoresist composition.

A monomer has the structure

##STR00001##

wherein R is an organic group comprising a polymerizable carbon-carbon double bond or carbon-carbon triple bond; X and Y are independently at each occurrence hydrogen or a non-hydrogen substituent; EWG1 and EWG2 are independently at each occurrence an electron-withdrawing group; p is 0, 1, 2, 3, or 4; n is 1, 2, 3, or 4; and M.sup.+ is an organic cation. A polymer prepared from monomer is useful as a component of a photoresist composition.

A monomer has the structure

##STR00001##

wherein R is an organic group comprising a polymerizable carbon-carbon double bond or carbon-carbon triple bond; X and Y are independently at each occurrence hydrogen or a non-hydrogen substituent; EWG1 and EWG2 are independently at each occurrence an electron-withdrawing group; p is 0, 1, 2, 3, or 4; n is 1, 2, 3, or 4; and M.sup.+ is an organic cation. A polymer prepared from monomer is useful as a component of a photoresist composition.

A polymer for resist use is obtainable from a hemiacetal compound having formula (1a) wherein R.sup.1 is H, CH.sub.3 or CF.sub.3, R.sup.2 to R.sup.4 each are H or a monovalent hydrocarbon group, X.sup.1 is a divalent hydrocarbon group, ZZ designates a non-aromatic mono- or polycyclic ring of 4 to 20 carbon atoms having a hemiacetal structure, k.sup.1=0 or 1, and k.sup.2=0 to 3. A resist composition comprising the polymer displays controlled acid diffusion and low roughness during both positive and negative tone developments. ##STR00001##

A polymer for resist use is obtainable from a hemiacetal compound having formula (1a) wherein R.sup.1 is H, CH.sub.3 or CF.sub.3, R.sup.2 to R.sup.4 each are H or a monovalent hydrocarbon group, X.sup.1 is a divalent hydrocarbon group, ZZ designates a non-aromatic mono- or polycyclic ring of 4 to 20 carbon atoms having a hemiacetal structure, k.sup.1=0 or 1, and k.sup.2=0 to 3. A resist composition comprising the polymer displays controlled acid diffusion and low roughness during both positive and negative tone developments. ##STR00001##

A polymer comprising recurring units having an acid generator bound to the backbone, and recurring units having an optionally acid labile group-substituted carboxyl group and/or recurring units having an optionally acid labile group-substituted hydroxyl group is obtained by polymerizing corresponding monomers under such illumination that the quantity of light of wavelength up to 400 nm is up to 0.05 mW/cm.sup.2. The polymer avoids photo-decomposition of the acid generator during polymerization and concomitant deprotection reaction of the acid labile group when used in positive resist compositions. A pattern with high dissolution contrast and rectangularity is formed after development.