Partially polymerized divinylsiloxane linked bisbenzocyclobutene resins and methods for making said resins

DETAILED DESCRIPTION OF THE INVENTION The DVS monomers of this invention include compounds of the structure: ##STR2## wherein each R.
sup.
3 is independently C.
sub.
1-6 alkyl, cycloalkyl, aralkyl, or phenyl; each R.
sup.
4 is independently ethenyl, propenyl or 2-methyl propenyl; each R.
sup.
5 is independently C.
sub.
1-6 alkyl, trimethylsilyl, methoxy, or chloro; each R.
sup.
6 is independently C.
sub.
1-6 alkyl, chloro, or cyano; n is an integer of 1 or more; and each q and r is independently an integer of zero or 1.
The most preferred DVS compound is represented by the formula: ##STR3## The depictions of this compound herein should not be construed to define any particular geometric isomer or spatial orientation about the ethenylene double bonds.
Compositions made by the processes disclosed herein contain positional isomers about these double bonds as well as other compounds.
These organopolysiloxane-bridged bisbenzocyclobutene monomers can be prepared by methods disclosed in U.
S.
Pat.
Nos.
4,812,588; 5,136,069; 5,138,081; and U.
S.
patent application Ser.
No.
677,023, filed Mar.
28, 1991.
Following one of the disclosed procedures for making the preferred DVS monomer, one will obtain a mixture containing as a major component divinyltetramethyldisiloxane-bis-benzocyclobutene monomer.
This monomer mixture has a low viscosity.
According to the process of the invention this DVS monomer may be partially polymerized in contact with a solvent.
One polymerizes the monomer under conditions that yield a partially polymerized resin that will yield acceptable performance when used as a photocurable resin in thin films.
Acceptable performance includes retention of integrity such as absence of crazing.
It also includes adequate film retention upon curing.
Crazing is the formation of fractures or wrinkling in the thin film of DVS resin as it is coated onto a substrate, as it is prebaked prior to photocuring or when it is exposed to a development solvent.
The fractures and wrinkling result in nonuniform thickness of the resin film