Pressure Sensitive Adhesives and Articles with Hyperbranched Silsesquioxane Core and Methods of Making the Same

Abstract

Pressure sensitive adhesives that include hyperbranched silsesquioxane-core polymers are described. Also described are various methods for producing the noted polymers and pressure sensitive adhesives. In addition, a variety of articles including tapes utilizing the pressure sensitive adhesives are described.

What is claimed is: 
     
         1 . A polymer comprising one or more hyperbranched polymers,
 the hyperbranched polymer exhibiting a core-shell structure comprising at least one silsesquioxane core and at least two polymer chains chemically bound to each of said at least one silsesquioxane cores, the shell comprising the at least two polymer chains,   wherein each of the at least two polymer chains originates from one silsesquioxane core to form one hyperbranched polymer such that one end of each polymer chain is chemically bound to the silsesquioxane core,   wherein the hyperbranched polymer is formed by a hydrolyzable and condensable, or only a condensable precursor, the precursor having a formula:
   R—Si(X) 3-a (Y) a  
 
   wherein R is one of a nonhydrolyzable organic group, a nonhydrolyzable oligomer chain, and a nonhydrolyzable polymer chain, X is a hydrolyzable group, Y is an organofunctional group, and the value of “a” is selected from the group consisting of 0, 1, 2, and combinations thereof,   wherein X is selected from the group consisting of halogen, acyloxy, ketoximate, alkoxy, and combinations thereof, and   wherein the molecular weight distribution (Mw/Mn) of the precursor is within a range of from 2.8 to 5.1.   
     
     
         2 . The polymer of  claim 1  wherein the precursor is a reaction product of a mixture comprising:
 (i) one or more (meth) acrylate monomers; 
 (ii) a free-radical initiator; and 
 (iii) a silane-bearing chain transfer agent (CTA); 
 wherein the mole ratio of the CTA to the initiator ranges from about 200:1 to about 1:2, 
 wherein the structure of the CTA is HS—R  SiX 3-a (Y) a    
 wherein R is an organic linking group situated between a thiol and a hydrolyzable silane moiety, X is a hydrolyzable group, Y is an organofunctional group, and the value of “a” is selected from the group consisting of 0, 1, 2, and combinations thereof, 
 wherein X is selected from the group consisting of halogen, acyloxy, ketoximate, alkoxy, and combinations thereof, and 
 wherein the initiator is activatable upon exposure to at least one of heat, actinic radiation, electron beam radiation, and combinations thereof. 
 
     
     
         3 . The polymer of  claim 2  wherein one or more of the following statements (A) to (F) applies:
 (A) the initiator is an actinic radiation activatable initiator; 
 (B) the initiator is a thermally activatable initiator; 
 (C) the mixture is free of a solvent; 
 (D) the mixture contains a solvent; 
 (E) the solvent is an inert theta solvent; or 
 (F) the reaction is a one-step reaction. 
 
     
     
         4 . The polymer of  claim 2  wherein one or more of the following statements (A) to (I) applies:
 (A) the precursor is hydrolyzable and condensable or only condensable at one of a temperature range of from about 20° C. to about 50° C. and from about 51° C. to about 170° C.; 
 (B) the hydrolysis and the condensation reactions, or only the condensation reaction, occurs in the presence of a catalyst and a core modifier; 
 (C) the catalyst is in the amount of from about 0.5 to about 5% by weight of the precursor; 
 (D) the core modifier has a formula selected from the group consisting of MX, MX 2 , MX 3 , MX 4 , MX 5 , MX 6 , RMX, RMX 2 , RMX 3 , RMX 4 , RMX 5 , and RMX 6 , in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, X is an alkoxide, and M is independently selected from the group consisting of Al, Ge, Sn, Ti, and Zr, and combinations thereof; 
 (E) the core modifier is a compound of the type RMX 3  in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, X is an alkoxide, and M is independently selected from the group consisting of Al, Ge, Sn, Ti, and Zr, and combinations thereof; 
 (F) the core modifier is a titanium alkoxide having the formula Ti(OR′) 4  in which R′ is selected from the group consisting of ethyl, isopropyl, butyl, acetylacetonate, and combinations thereof; 
 (G) the hydrolysis and the condensation reactions, or only the condensation reaction, occurs in the presence of a solvent; 
 (H) the solvent is an inert theta solvent; or 
 (I) the hydrolysis and the condensation reactions, or only the condensation, reaction occurs in the absence of a solvent (solvent-free). 
 
     
     
         5 . The polymer of  claim 1  further including a tackifier. 
     
     
         6 . The polymer of  claim 1  wherein each one of the silsesquioxane cores of a portion of the hyperbranched polymers is serially and covalently linked to at least one other silsesquioxane core to form a pearl chain structure. 
     
     
         7 . The polymer of  claim 6  wherein the link comprises a polyol having a structure 
       
         
           
           
               
               
           
         
       
       where R is a spacer group situated between the OH groups, and n is selected from the group consisting of 2, 3, 4, and combinations thereof. 
     
     
         8 . The polymer of  claim 1  wherein each one of the silsesquioxane cores of a portion of the hyperbranched polymers is covalently linked to at least one other silsesquioxane core to form a multidimensional network structure. 
     
     
         9 . The polymer of  claim 8  wherein one or both of the following statements (A)-(B) apply:
 (A) the link comprises a hydrolyzable di-silane having a structure
   (Y) a X 3-a Si R SiX 3-a (Y) a    
 
 where R is an organic group situated between the two hydrolyzable silane moieties, X is a hydrolyzable group, Y is an organofunctional group, and each ‘a’ is independently selected from 0, 1, and 2; or 
 (B) the multidimensional network is a two and/or three dimensional structure. 
 
     
     
         10 . A method of forming a polymer comprising the steps of:
 providing the precursor according to  claim 1 ; and   subjecting the precursor to a hydrolysis and a condensation reaction or only a condensation reaction to thereby form a hyperbranched polymer, the hyperbranched polymer exhibiting a core-shell structure comprising at least one silsesquioxane core and at least two polymer chains chemically bound to each of said at least one silsesquioxane cores, the shell comprising the at least two polymer chains,   wherein each of the at least two polymer chains originates from one silsesquioxane core to form one hyperbranched polymer such that one end of each polymer chain is chemically bound to the silsesquioxane core.   
     
     
         11 . The method of  claim 10  wherein the step of providing a precursor comprises polymerizing (meth)acrylate monomers in the presence of a free-radical initiator and a silane-bearing chain transfer agent (CTA),
 wherein one or both of the following statements (A)-(B) apply: 
 (A) the mole ratio of CTA to initiator ranges from 200:1 to 1:2; 
 (B) the structure of the chain transfer agent (CTA) is HS—R SiX 3-a (Y) a    
 wherein R is an organic linking group situated between a thiol and a hydrolyzable silane moiety, X is a hydrolyzable group, Y is an organofunctional group, and the value of “a” is selected from the group consisting of 0, 1, 2, and combinations thereof, 
 wherein X is selected from the group consisting of halogen, acyloxy, ketoximate, alkoxy, and combinations thereof. 
 
     
     
         12 . The method of  claim 11  wherein the initiator is activated upon exposure to at least one of heat, actinic radiation, electron beam radiation, and combinations thereof. 
     
     
         13 . The method of  claim 10  wherein the hydrolysis and the condensation reactions, or only the condensation reaction, occurs at one of a temperature range of from about 20° C. to about 50° C. and from about 51° C. to about 170° C.,
 wherein the hydrolysis and the condensation reactions, or only the condensation, reaction occurs in the presence of a catalyst, and 
 wherein the catalyst is in the amount of from about 0.5 to about 5% by weight of the precursor. 
 
     
     
         14 . The method of any one of  claim 10  further comprising:
 providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction. 
 
     
     
         15 . The method of  claim 10  further including the step of adding a tackifier,
 wherein the tackifier is substantially compatible with the precursor. 
 
     
     
         16 . The method of  claim 10  further including the step of adding an amount of a polyol during the condensation reaction to serially and covalently link each one of the silsesquioxane cores of a portion of the hyperbranched polymers to another silsesquioxane core to form a pearl chain structure. 
     
     
         17 . The method of  claim 16  wherein the polyol having a structure 
       
         
           
           
               
               
           
         
       
       where R is a spacer group situated between the OH groups, and n is selected from the group consisting of 2, 3, 4, and combinations thereof,
 wherein the polyol is in the amount of from about 0 to about 30% by weight of at least one of the hyperbranched polymer and the polymer. 
 
     
     
         18 . The method of  claim 10  further including the step of adding an amount of a hydrolyzable di-silane during the condensation reaction to link each one of the silsesquioxane cores of a portion of the hyperbranched polymers to at least one other silsesquioxane core to form a multidimensional network structure. 
     
     
         19 . The method of  claim 18  wherein the hydrolyzable di-silane having a structure
   (Y) a x 3-a si R SiX 3-a (Y) a    
 where R is an organic group situated between the two hydrolyzable silane moieties, X is a hydrolyzable group, Y is an organofunctional group, and each ‘a’ is independently selected from 0, 1, and 2, 
 wherein any one or more of the following statements (A)-(C) apply: 
 (A) the multidimensional network is a two and/or three dimensional structure; 
 (B) the hydrolyzable di-silane is in the amount of from about 0 to about 30% by weight of at least one of the hyperbranched polymer and the polymer; or 
 (C) X is selected from the group consisting of halogen, acyloxy, ketoximate, alkoxy, and combinations thereof. 
 
     
     
         20 . A pressure sensitive adhesive comprising the polymer formed from the method of  claim 10 . 
     
     
         21 . A pressure sensitive adhesive comprising the polymer of  claim 1 . 
     
     
         22 . The polymer of  claim 1  wherein any one of the following statements (A)-(BB) applies:
 (A) each of the at least two polymer chains originates from one silsesquioxane core to form one hyperbranched polymer such that one end of each polymer chain is chemically bound to the silsesquioxane core while allowing the other end of the chain to dangle freely; 
 (B) the hyperbranched polymer is a discrete molecule; 
 (C) the precursor has a single terminal silane unit or group; 
 (D) the polymer chain does not contain any ethylenic unsaturation or acrylate unsaturation along the backbone of the polymer chain; 
 (E) the polymer chains are free of crosslinking; 
 (F) the polymer chains do not contain reactive groups that can facilitate crosslinking using triggers selected from the group consisting of heat, moisture, ultraviolet, electron beam, and combinations thereof; 
 (G) the silsesquioxane core is selected from the group consisting of a pure silsesquioxane core, a hybrid silsesquioxane core, and combinations thereof; 
 (H) the silsesquioxane core is selected from the group consisting of a fully condensed core, a partially condensed core, and combinations thereof; 
 (I) the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of MX, MX 2 , MX 3 , MX 4 , MX 5 , MX 6 , RMX, RMX 2 , RMX 3 , RMX 4 , RMX 5 , and RMX 6 , in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, M is independently selected from the group consisting of Al, Si, Ge, Sn, Ti, Zr, and combinations thereof, and X is selected from the group consisting of organic monodentate ligand, organic bidentate ligand, organic tridentate ligand, organic ambidentate ligand, halogen, alkoxide, and combinations thereof; 
 (J) the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of M(X) 4  and M(X) a (Z) b  in which M is independently selected from the group consisting of Al, Si, Ge, Sn, Ti, Zr, and combinations thereof, a is 2, b is 2, X is a hydrolyzable group, Z is an organic ligand of the formula A-C(O)—(R′) n —C(O)—B wherein R′ is an organic group and n is an integer from 0 to 10, A is an organic group, and B is an organic group; 
 (K) the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with another Si atom of a core modifier, the core modifier having a formula R″ 4-q Si(OR #) q  wherein R″ is a functional or non-functional hydrocarbon group, R # is selected from the group consisting of methyl, ethyl, and isopropyl, and combinations thereof, and q is 2 or 3; 
 (L) the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with another Si atom of a core modifier, the core modifier having a formula Si(OR #) 4  in which R # is selected from the group consisting of methyl, ethyl, isopropyl, and combinations thereof; 
 (M) the silsesquioxane core comprises a hybrid core selected from the group consisting of: 
 (i) a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of MX, MX 2 , MX 3 , MX 4 , MX 5 , MX 6 , RMX, RMX 2 , RMX 3 , RMX 4 , RMX 5 , and RMX 6 , in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, M is independently selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof, and X is selected from the group consisting of organic monodentate ligand, organic bidentate ligand, organic tridentate ligand, organic ambidentate ligand, halogen, alkoxide, and combinations thereof; and 
 (ii) a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of M(X) 4  and M(X) a (Z) b  in which M is independently selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof, a is 2, b is 2, X is a hydrolyzable group, Z is an organic ligand of the formula A-C(O)—(R′) n —C(O)—B wherein R′ is an organic group and n is an integer from 0 to 10, A is an organic group, and B is an organic group. 
 (N) the fully condensed silsesquioxane cores have the general formula [RSiO 3/2 ] n  where n is an even number and R is selected from the group consisting of alkyl, aryl, heterocarbon, polymer chain, oligomer chain, (meth)acrylate polymer chain, (meth)acrylate oligomer chain, and combinations thereof; 
 (O) the silsesquioxane core is a structure in which each member silicon atom is linked to three other member silicon atoms through oxygen atoms and/or a structure in which at least one silicon atom is linked to no more than two other member silicon atoms through oxygen atoms; 
 (P) the silsesquioxane core is in at least one of a caged form, polymeric form, ladder structure, and combinations thereof; 
 (Q) the silsesquioxane core is a two and/or three dimensional structure; 
 (R) each of the polymer chains comprises polymers selected from the group consisting of compositionally different polymer chains, compositionally the same polymer chains, and combinations thereof; 
 (S) the polymer chain comprises (meth)acrylate monomers linked to form polymers selected from the group consisting of linear homopolymers, branched homopolymers, linear copolymers, branched copolymers, and combinations thereof; 
 (T) at least one of the hyperbranched polymer and the polymer comprises at least 50% by weight of (meth)acrylate monomers. 
 (U) the polymer further includes an oligomer having at least one crosslinkable functional group, 
 wherein the oligomer is a liquid at room temperature, and 
 wherein the oligomer has a backbone selected from the group consisting of polyether, polyisobutylene, amorphous poly-alpha olefins, polybutadienes, polyisoprenes, polydimethylsiloxanes, polyalkyloxazolines, polyesters, poly(methyl)acrylates, polyurethanes, and combinations thereof; 
 (V) the number average molecular weight (Mn) of the precursor is within a range of from 2,000 to 300,000 g/mole as determined by gel permeation chromatography; 
 (W) the number average molecular weight (Mn) of the precursor is within a range of from 59,495 to 300,000 g/mole as determined by gel permeation chromatography; 
 (X) the number average molecular weight (Mn) of the precursor is within a range of from 30,078 to 88,024 g/mole determined by gel permeation chromatography; 
 (Y) the number average molecular weight (M n ) of the polymer is within a range of from about 20,000 to about 1,000,000 g/mole as determined by gel permeation chromatography; 
 (Z) the polymer exhibits a glass transition temperature (Tg) of from 10° C. to −60° C. as determined by differential scanning calorimetry (DSC); 
 (AA) the polymer exhibits a plateau shear modulus at 25° C. and 1 radian per second that is between 5×10 4  and 6×10 6  dynes/cm 2  as determined by dynamic mechanical analysis (DMA); 
 (BB) the core comprises one or more silicon atoms in the core substituted with atom M, wherein atom M comprises an element selected from the group consisting of metals, metalloids, and combinations thereof; 
 wherein the metalloids exclude Si; or 
 wherein atom M comprises a transition metal; or 
 wherein atom M comprises a metal selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof; 
 wherein atom M comprises a metal selected from the group consisting of Na′, Be 2+ , and combinations thereof; and/or 
 wherein a mole ratio of metal content M to the silicon content in the silsesquioxane core is no greater than 30:1. 
 
     
     
         23 . The method of  claim 8  wherein any one of the following statements (A)-(BB) applies:
 (A) each of the at least two polymer chains originate from one silsesquioxane core to form one hyperbranched polymer such that one end of each polymer chain is chemically bound to the silsesquioxane core while allowing the other end of the chain to dangle freely; 
 (B) the hyperbranched polymer is a discrete molecule; 
 (C) the precursor has a single terminal silane unit or group; 
 (D) the polymer chain does not contain any ethylenic unsaturation or acrylate unsaturation along the backbone of the polymer chain; 
 (E) the polymer chains are free of crosslinking; 
 (F) the polymer chains do not contain reactive groups that can facilitate crosslinking using triggers selected from the group consisting of heat, moisture, ultraviolet, electron beam, and combinations thereof; 
 (G) the silsesquioxane core is selected from the group consisting of a pure silsesquioxane core, a hybrid silsesquioxane core, and combinations thereof; 
 (H) the silsesquioxane core is selected from the group consisting of a fully condensed core, a partially condensed core, and combinations thereof; 
 (I) the method further comprising providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction, wherein the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of MX, MX 2 , MX 3 , MX 4 , MX 5 , MX 6 , RMX, RMX 2 , RMX 3 , RMX 4 , RMX 5 , and RMX 6 , in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, M is independently selected from the group consisting of Al, Si, Ge, Sn, Ti, Zr, and combinations thereof, and X is selected from the group consisting of organic monodentate ligand, organic bidentate ligand, organic tridentate ligand, organic ambidentate ligand, halogen, alkoxide, and combinations thereof; 
 (J) the method further comprising providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction, wherein the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of M(X) 4  and M(X) a (Z) b  in which M is independently selected from the group consisting of Al, Si, Ge, Sn, Ti, Zr, and combinations thereof, a is 2, b is 2, X is a hydrolyzable group, Z is an organic ligand of the formula A-C(O)—(R′) n —C(O)—B wherein R′ is an organic group and n is an integer from 0 to 10, A is an organic group, and B is an organic group; 
 (K) the method further comprising providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction, wherein the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with another Si atom of a core modifier, the core modifier having a formula R″ 4-q Si(OR #) q  wherein R″ is a functional or non-functional hydrocarbon group, R # is selected from the group consisting of methyl, ethyl, isopropyl, and combinations thereof, and q is 2 or 3; 
 (L) the method further comprising providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction, wherein the silsesquioxane core comprises a hybrid core having one or more of the Si atoms in the core substituted with another Si atom of a core modifier, the core modifier having a formula Si(OR #) 4  in which R # is selected from the group consisting of methyl, ethyl, isopropyl, and combinations thereof; 
 (M) the method further comprising providing a core modifier prior to and/or during the subjecting of the precursor to the hydrolysis and the condensation reactions, or only the condensation reaction, wherein the silsesquioxane core comprises a hybrid core selected from the group consisting of: 
 (i) a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of MX, MX 2 , MX 3 , MX 4 , MX 5 , MX 6 , RMX, RMX 2 , RMX 3 , RMX 4 , RMX 5 , and RMX 6 , in which R is selected from the group consisting of alkyl, alkenyl, aryl, H, and combinations thereof, M is independently selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof, and X is selected from the group consisting of organic monodentate ligand, organic bidentate ligand, organic tridentate ligand, organic ambidentate ligand, halogen, alkoxide, and combinations thereof; and 
 (ii) a hybrid core having one or more of the Si atoms in the core substituted with atom M of a core modifier, the core modifier having a formula selected from the group consisting of M(X) 4  and M(X) a (Z) b  in which M is independently selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof, a is 2, b is 2, X is a hydrolyzable group, Z is an organic ligand of the formula A-C(O)—(R′) n —C(O)—B wherein R′ is an organic group and n is an integer from 0 to 10, A is an organic group, and B is an organic group; 
 (N) the fully condensed silsesquioxane cores have the general formula [RSiO 3/2 ] n  where n is an even number and R is selected from the group consisting of alkyl, aryl, heterocarbon, polymer chain, oligomer chain, (meth)acrylate polymer chain, (meth)acrylate oligomer chain, and combinations thereof; 
 (O) the silsesquioxane core is a structure in which each member silicon atom is linked to three other member silicon atoms through oxygen atoms and/or a structure in which at least one silicon atom is linked to no more than two other member silicon atoms through oxygen atoms; 
 (P) the silsesquioxane core is in at least one of a caged form, polymeric form, ladder structure, and combinations thereof; 
 (Q) the silsesquioxane core is a two and/or three dimensional structure; 
 (R) each of the polymer chains comprises polymers selected from the group consisting of compositionally different polymer chains, compositionally the same polymer chains, and combinations thereof; 
 (S) the polymer chain comprises (meth)acrylate monomers linked to form polymers selected from the group consisting of linear homopolymers, branched homopolymers, linear copolymers, branched copolymers, and combinations thereof; 
 (T) at least one of the hyperbranched polymer and the polymer comprises at least 50% by weight of (meth)acrylate monomers. 
 (U) the polymer further includes an oligomer having at least one crosslinkable functional group, 
 wherein the oligomer is a liquid at room temperature, and 
 wherein the oligomer has a backbone selected from the group consisting of polyether, polyisobutylene, amorphous poly-alpha olefins, polybutadienes, polyisoprenes, polydimethylsiloxanes, polyalkyloxazolines, polyesters, poly(methyl)acrylates, polyurethanes, and combinations thereof; 
 (V) the number average molecular weight (Mn) of the precursor is within a range of from 2,000 to 300,000 g/mole as determined by gel permeation chromatography; 
 (W) the number average molecular weight (Mn) of the precursor is within a range of from 59,495 to 300,000 g/mole as determined by gel permeation chromatography; 
 (X) the number average molecular weight (Mn) of the precursor is within a range of from 30,078 to 88,024 g/mole determined by gel permeation chromatography; 
 (Y) the number average molecular weight (Mn) of the polymer is within a range of from about 20,000 to about 1,000,000 g/mole as determined by gel permeation chromatography; 
 (Z) the polymer exhibits a glass transition temperature (Tg) of from 10° C. to −60° C. as determined by differential scanning calorimetry (DSC); 
 (AA) the polymer exhibits a plateau shear modulus at 25° C. and 1 radian per second that is between 5×10 4  and 6×10 6  dynes/cm 2  as determined by dynamic mechanical analysis (DMA); 
 (BB) the core comprises one or more silicon atoms in the core substituted with atom M, wherein atom M comprises an element selected from the group consisting of metals, metalloids, and combinations thereof; 
 wherein the metalloids exclude Si; or 
 wherein atom M comprises a transition metal; or 
 wherein atom M comprises a metal selected from the group consisting of Al, Ge, Sn, Ti, Zr, and combinations thereof; 
 wherein atom M comprises a metal selected from the group consisting of Na′, Li′, Be″, and combinations thereof; and/or 
 wherein a mole ratio of metal content M to the silicon content in the silsesquioxane core is no greater than 30:1. 
 
     
     
         24 . An article comprising the pressure sensitive adhesive of  claim 21 , wherein the article further comprises:
 a substrate defining a face;   wherein the pressure sensitive adhesive is disposed on at least a portion of the face of the substrate.   
     
     
         25 . An article comprising the pressure sensitive adhesive formed from the method of  claim 10 , wherein the article further comprises:
 a substrate defining a face;   wherein the pressure sensitive adhesive is disposed on at least a portion of the face of the substrate.