Photopolymerizable and photocleavable resins and low shrink and low stress composite compositions

2) As claimed in 1, such reactive and photoresponsive moiety more preferably can be α-hydroxyalkylphenone (HP) or any other functional photoresponsive moiety.

3) As claimed in 1, such P&P resin monomer can be constructed via any linkages such as ester, carbonate, urea, urethane, ether et al.

4) As claimed in 1, such P&P resin monomer have to bear at least two photopolymerizable groups.

5) As claimed in 2, the photopolymerizable group can by vinyl, vinylether, acrylate, methacrylate, or their combination.

6) As claimed in 1, such photopolymerizable and photocleavable (P&P) resin monomer can be liquid and/or semicrystalline solid.

7) As claimed in 6, the photopolymerizable and photocleavable (P&P) resin monomer can be used with any other conventional resins including BisGMA, TEGDMA, UDMA, et al.

8) As claimed in 7, the content of such photopolymerizable and photocleavable (P&P) resin monomer in other resin mix range from 1% to 99%, preferably 20-70%, more preferably 30-50%, wt/wt/.

9) As claimed in 3, various coupling agents such as primary diols, diamine, diacid, diusocynate, et al can be used.

10) As claimed in 9, the coupling agent could aliphatic or aromatic or both

11) As claimed in 10, the different coupling agent could be used.

12) As claimed in 11, different amounts of agents could be used to control viscosity of the resulting P&P resin monomers.

13) As claimed in 12, inert polymerizable resin could be introduced to control viscosity.