Photopolymerizable dental composites with rapid curing and low shrinkage stress

A radically polymerizable material, comprising

• (a) 0.01 to 5 wt.-% of at least one transfer reagent,
• (b) 5 to 60 wt.-% of at least one multifunctional (meth)acrylate or of a mixture of mono- and multifunctional (meth)acrylates,
• (c) 0.01 to 3.0 wt.-% of a mixture of at least one monomolecular and at least one bimolecular photoinitiator,
• (d) 30 to 90 wt.-% of at least one filler, and
• (e) optionally additive(s), in each case relative to the total mass of the material,
• wherein the at least one monomolecular photoinitiator comprises a tetraacylgermanium compound,
• wherein the material comprises as transfer reagent (a) at least one allyl sulfone of Formula I
• in which the variables have the following meanings:
• A H;
• —CN;
• a phenyl radical, which can bear one or more substituents, such as —CH3, —C2H5, —OH, —OCH3, —O—COCH3, a polymerizable vinyl, (meth)acryloyloxy or (meth)acrylamide group, or an aliphatic linear or branched C1-C20 alkylene or C1-C20 alkyl radical, which can be interrupted by one or more 1,4-phenylene groups, urethane groups, O or S, which can bear one or more substituents, such as —OH or —OCH3, and which can bear a tri-C1-C4 alkoxysilyl group or a polymerizable vinyl, (meth)acryloyloxy or (meth)acrylamide group terminally;
• R1 in each case independently of one another H, an aliphatic linear or branched C1-C9 alkyl radical, tolyl or phenyl;
• R2 in each case independently of one another a phenyl radical, which can bear one or more substituents, such as —CH3, —C2H5, —OH, —OCH3, —O—COCH3, a polymerizable vinyl, (meth)acryloyloxy or (meth)acrylamide group, —C(═CH2)—COOR3 or —C(═CH2)—CO—NR4R5;
• or an aliphatic linear or branched C1-C20 alkyl radical, which can be interrupted by O or S and which can bear a polymerizable vinyl, (meth)acryloyloxy or (meth)acrylamide group, —C(═CH2)—COOR3 or —C(═CH2)—CO—NR4R5 terminally, wherein R3-5 independently of one another are in each case a linear or branched C1-6 alkyl radical;
• X —COO—, —CON(R6)— or is absent, wherein the bonding to A is effected via O or N and wherein
• R6 is H;
• or an aliphatic linear or branched C1-C20 alkyl radical, which can be interrupted by one or more O or S and which can bear a polymerizable vinyl, (meth)acryloyloxy or (meth)acrylamide group, —C(═CH2)—COOR3 or —C(═CH2)—CO—NR4R5 terminally, wherein R3-5 independently of one another are in each case a linear or branched C1-6 alkyl radical;
• n an integer from 1 to 6,
• a vinyl sulfone ester of Formula II,
• in which the variables have the following meanings:
• B H, CN, a cycloaliphatic, linear or branched aliphatic C1-C30 hydrocarbon radical, which can be substituted by one or more substituents, which can be interrupted by one or more urethane groups, ester groups, O and/or S and which can contain 1 to 4 benzene groups,
• an aromatic C6-C30 hydrocarbon radical, which can be substituted by one or more substituents,
• or a combination thereof;
• Y —COO—, —CON(R7)— or is absent, wherein the bonding to B is effected via O or N;
• C a cycloaliphatic, linear or branched aliphatic C1-C30 hydrocarbon radical, which can be substituted by one or more substituents, which can be interrupted by one or more urethane groups, ester groups, O and/or S and which can contain 1 to 4 benzene groups,
• an aromatic C6-C30 hydrocarbon radical, which can be substituted by one or more substituents,
• or a combination thereof;
• R7 hydrogen, a cycloaliphatic, linear or branched aliphatic C1-C10 hydrocarbon radical, which can be interrupted by one or more oxygen atoms and which can be substituted by one or more OH groups, or
• an aromatic C6-C10 hydrocarbon radical, which can be substituted by one or more OH groups;
• p an integer from 1 to 6;
• k an integer from 1 to 6;
• q an integer from 1 to 6;
• wherein
• p and q cannot be greater than 1 at the same time and wherein if p=1, q=k, and if q=1, p=k;
• and
• wherein the material does not contain a monoacylphosphine oxide, a bisacylphosphine oxide or a mixture thereof.