A resin composition contains a 2-methylene-1,3-dicarbonyl compound and an initiator. The 2-methylene-1,3-dicarbonyl compound has a molecular weight of 180 to 10,000, and the initiator contains a basic substance having a pK.sub.a of 8 or greater. The 2-methylene-1,3-dicarbonyl compound contains a structural unit represented by the following formula (I)

##STR00001##

A resin composition contains a 2-methylene-1,3-dicarbonyl compound and an initiator. The 2-methylene-1,3-dicarbonyl compound has a molecular weight of 180 to 10,000, and the initiator contains a basic substance having a pK.sub.a of 8 or greater. The 2-methylene-1,3-dicarbonyl compound contains a structural unit represented by the following formula (I)

##STR00001##

Polymerizable compositions comprising a redox initiator system is disclosed. The redox initiator system comprises a photolabile transition metal complex that photolyzes and initiates the redox cycle. Dental compositions comprising dental resins and the photolabile redox initiator system are also described.

The present invention provides a nitrile group-containing highly-saturated copolymer rubber comprising an ,-ethylenically unsaturated nitrile monomer unit (a) in a content of 28 wt % or more and a conjugated diene monomer unit (b) in a content of 20 to 72 wt %, and having an iodine value of 120 or less, wherein the conjugated diene monomer unit (b) is at least partially hydrogenated, and a proportion of an isoprene unit in the conjugated diene monomer unit (b) is 33 wt % or more.

The present invention provides a nitrile group-containing highly-saturated copolymer rubber comprising an ,-ethylenically unsaturated nitrile monomer unit (a) in a content of 28 wt % or more and a conjugated diene monomer unit (b) in a content of 20 to 72 wt %, and having an iodine value of 120 or less, wherein the conjugated diene monomer unit (b) is at least partially hydrogenated, and a proportion of an isoprene unit in the conjugated diene monomer unit (b) is 33 wt % or more.

A shape-programmable liquid crystal elastomer comprises polymerized, nematic monomers. The monomers are organized into a plurality of voxels with each voxel having a director orientation.

A shape-programmable liquid crystal elastomer comprises polymerized, nematic monomers. The monomers are organized into a plurality of voxels with each voxel having a director orientation.

Compounds of formula (I) are photoinitiators or photosensitizers in a photopolymerizable composition:

##STR00001##

R.sub.1 represents a monovalent, linear, branched or cyclic, aliphatic hydrocarbon group having 1 to 20 carbon atoms, optionally substituted with substituent(s) selected from Cl, Br, OH, O, NHCO OR.sub.2, NHCOR.sub.2 or free-radically or ionically polymerizable groups. Each R.sub.2 is independently H or C.sub.1-6 alkyl; n is 1. If n=1, Z and Y are absent and X represents OR.sub.3; if n is >1, Z represents OR.sub.4, Y represents ORs and X represents H or OH. R.sub.3 represents H or R.sub.1; and R.sub.4 and R.sub.5 each independently represent a bivalent hydrocarbon group. The polymerizable moieties as optional substituents of R.sub.1 are polymerizable double or triple bonds, lactam, lactone and epoxide moieties, which are subjectable to ring-opening polymerization; and two of R.sub.1 to R.sub.5 may be linked to one another to form a ring or a dimer.

The invention relates to the use of a branched polyester having an average of at least 2.8 terminal groups as additive for a curable pre-polymer composition, wherein the branched polyester acts as de-foaming agent.

A radiation curable composition including at least one radiation hardenable component, a photo-initiator, and a filler material having a population of particulates in an amount greater than or equal to 50% by weight of the printable composition. The population of particulates exhibits a median diameter (D50) of greater than or equal to 0.3 micrometer on a volume-average basis as determined using the Particle Size Test Method, and the radiation curable composition exhibits a viscosity of less than or equal to 150 Pa s when measured using the Viscosity Test Method. A method, apparatus, and systems for producing composite articles by selectively exposing a portion of the radiation curable composition to a source of actinic radiation to at least partially cure the exposed portion of the radiation curable composition, thereby forming a hardened layer, preferably by an additive manufacturing process such as stereophotolithography, are also described. The composite articles may include composite dental restorations.