Methods and systems for recovering dicyclopentadiene from pygas are provided. Methods can include heating pygas to generated heated pygas, recovering a C.sub.5 fraction from the heated pygas, and dimerizing cyclopentadiene from the C.sub.5 fraction to form dicyclopentadiene. Methods can further include recovering the C.sub.5 fraction from the pygas in a depentanizer column. Other methods can include heating pygas including dicyclopentadiene to form cyclopentadiene and hydrogenating cyclopentadiene in the pygas to form cyclopentane.

A polyphenylene ether oligomer and a polyphenylene ether oligomer are provided. The polyphenylene ether oligomer has a structure represented by Formula (I): ##STR00001## wherein each R.sup.1 can be independently hydrogen, C.sub.1-6 alkyl group, or phenyl group; each R.sup.2 can be independently hydrogen, C.sub.1-6 alkyl group, or phenyl group; a:(a+b) is from 0.05:1 to 1:1; n:(a+b) is from 0.05:1 to 5:1; Q can be ##STR00002##
m can be 0 or an integer from 1 to 4; Ra can be C.sub.1-6 alkylene group; Rb can be C.sub.1-6 alkylene group; each X is independently hydrogen, acryloyl group, allyl group, vinylbenzyl group, epoxypropyl group, methacryloyl group, propargyl group, or cyanol group; and wherein the polyphenylene ether oligomer can have a number average molecular weight from 400 to 2,000.

An onium salt having formula (1) is provided. A chemically amplified resist composition comprising the onium salt as a PAG has advantages including high solvent solubility, high sensitivity, a high contrast, and improved lithography properties such as EL and LWR when processed by photolithography using high-energy radiation.

##STR00001##

Disclosed herein are embodiments of methods for making and using functionalized forms of polydicyclopentadiene polymers. The disclosed polymers and methods enable a greater range of uses than the unmodified polydicyclopentadiene, which is currently used industrially. In addition, the presence of the functional groups contemplated by the disclosed compounds and formulae allow for the control of the polymer surface energy, and also enables the use of reversible chemical crosslinks, which permits recycling of the material.

Dicyclopentadiene (DCPD) derivatives of following general formula (I); their preparation and use thereof, especially as monomers in polymerization reactions, such as olefin polymerization or ring-opening metathesis polymerization (ROMP).

##STR00001##

A resist composition comprising a base polymer and a sulfonium salt of iodized benzoic acid offers a high sensitivity and minimal LWR independent of whether it is of positive or negative tone.

A resist composition comprising a base polymer and a sulfonium salt of iodized benzoic acid offers a high sensitivity and minimal LWR independent of whether it is of positive or negative tone.

A dynamic process for purifying dicyclopentadiene from a mixed liquid hydrocarbon stream comprising dicyclopentadiene and one or more of a C.sub.5 paraffin, a C.sub.5 olefin, co-dimers, cyclopentadiene, benzene, vinyl norbornene, bicyclononadiene, propenyl norbornene, isopropenyl norbornene, methylbicyclononadiene, methyldicyclopentadiene, and various minor organic impurities is introduced, wherein the dicyclopentadiene is separated from the mixed liquid hydrocarbon stream by melt crystallizing sweating and collecting dicyclopentadiene.

Disclosed herein are embodiments of methods for making and using functionalized forms of polydicyclopentadiene polymers. The disclosed polymers and methods enable a greater range of uses than the unmodified polydicyclopentadiene, which is currently used industrially. In addition, the presence of the functional groups contemplated by the disclosed compounds and formulae allow for the control of the polymer surface energy, and also enables the use of reversible chemical crosslinks, which permits recycling of the material.

A process for inhibiting the polymerization of cyclopentadiene compounds (B) by contacting the cyclopentadiene compound with a quinone methide compound (A) of structure (I), ##STR00001## Compositions (AB) comprising (A) and (B) are also provided.