Curable compositions for use as adhesives having properties capable of being altered based on external stimuli and methods of making and using the same

A method for bonding two substrates with an adhesive comprising the steps of:

• applying a curable composition to a first substrate, wherein the curable composition comprises:
• a) at least one urethane (meth)acrylate oligomer having a structure comprising:
• a1) at least one polyol backbone segment having at least one reacted end;
• a2) at least one reacted polyisocyanate forming a urethane linkage at the at least one reacted end of each of said at least one polyol backbone segment;
• and
• a3) at least one blocking end group reacted with said at least one reacted polyisocyanate to form a reversible bond, and wherein said at least one blocking end group bears a (meth)acrylate group;
• b) either:
• b1) a monofunctional chain terminator or
• b2) a polyfunctional chain extender and
• c) optionally, at least one monofunctional ethylenically unsaturated monomer or oligomer different from a);
• curing the curable composition to form the adhesive having a first set of adhesive properties;
• contacting a second substrate with the adhesive to bond the second substrate with the first substrate;
• and
• externally stimulating the cured composition to impart a second set of adhesive properties to the adhesive, different from the first set of adhesive properties.

A curable composition comprising:

• a) at least one urethane (meth)acrylate oligomer having a structure comprising:
• a1) at least one polyol backbone segment having at least one reacted end, wherein the polyol comprises a blend of a high molecular weight polyester and a low molecular weight polyester and the ratio of high molecular weight polyester to low molecular weight polyester ranges from about 1:8 to 3:1;
• a2) at least one reacted polyisocyanate forming a urethane linkage at the at least one reacted end of each of said at least one polyol backbone segment;
• and
• a3) at least one blocking end group reacted with said at least one reacted polyisocyanate to form a reversible bond and wherein said at least one blocking end group bears a (meth)acrylate group;
• b) either:
• b1) a monofunctional chain terminator or
• b2) a polyfunctional chain extender and
• c) optionally, at least one monofunctional ethylenically unsaturated monomer or oligomer different from a),
• wherein the at least one urethane (meth)acrylate oligomer has a molecular weight distribution having two primary peaks comprising a lower molecular weight peak in a range of 800 to 1,500 g/mol and a higher molecular weight peak in a range of 6,000 to 12,000 g/mol.

A curable composition comprising:

• a) at least one urethane (meth)acrylate oligomer having a structure comprising:
• a1) at least one polyol backbone segment having at least one reacted end, wherein the polyol comprises a polyester;
• a2) at least one reacted polyisocyanate forming a urethane linkage at the at least one reacted end of each of said at least one polyol backbone segment;
• and
• a3) at least one blocking end group reacted with said at least one reacted polyisocyanate to form a reversible bond and wherein said at least one blocking end group bears a (meth)acrylate group;
• b) a polyfunctional chain extender comprising a difunctional reactant and a trifunctional reactant, wherein the weight ratio of the trifunctional reactant to the difunctional reactant is between about 1:1,000 and about 1:20 and
• c) optionally, at least one monofunctional ethylenically unsaturated monomer or oligomer different from a),
• wherein the at least one urethane (meth)acrylate oligomer has a molecular weight distribution having two primary peaks comprising a lower molecular weight peak in a range of 800 to 1,500 g/mol and a higher molecular weight peak in a range of 6,000 to 12,000 g/mol.