Crosslinked polyolefins for biomedical applications and method of making same
A method for preparing a copolymer that involves polymerizing at least one branched alkene monomer and at least one olefin monomer having a pendant benzocyclobutene (BCB) group to form a copolymer comprising a random distribution of a plurality of constitutional units corresponding to the at least one branched alkene monomer and the at least one olefin monomer. The polymerizing includes a carbocationic polymerization reaction involving sequential addition of a plurality of mixtures without terminating the carbocationic polymerization reaction, wherein the plurality of mixtures includes a mixture that includes the at least one branched alkene monomer and does not include the at least one olefin monomer having a pendant BCB group and a mixture that includes both the at least one branched alkene monomer and the at least one olefin monomer having a pendant BCB group. The copolymer composition can undergo crosslinking at elevated temperatures (preferably above 180° C.).
1. A method of preparing a copolymer comprising:
polymerizing at least one branched alkene monomer and at least one olefin monomer having a pendant benzocyclobutene (BCB) group to form a copolymer comprising a random distribution of a plurality of constitutional units that include constitutional units corresponding to the at least one branched alkene monomer and constitutional units corresponding to the at least one olefin monomer having a pendant BCB group;
wherein the polymerizing includes a carbocationic polymerization reaction involving i) forming a mixture that includes the at least one branched alkene monomer and at least one initiator compound to initiate a polymerization reaction of the at least one branched alkene monomer, wherein the mixture does not include the at least one olefin monomer having a pendant BCB group, and ii) adding both the at least one branched alkene monomer and the at least one olefin monomer having a pendant BCB group to the polymerization reaction of i) without terminating the carbocationic polymerization reaction.
2. A method according to claim 1 , wherein:
the first mixture further includes at least one solvent.
3. A method according to claim 1 , wherein:
the at least one branched alkene monomer comprises an isoolefin selected from the group consisting of isobutylene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, and combinations thereof.
4. A method according to claim 1 , wherein:
the at least one branched alkene monomer comprises isobutylene.
5. A method according to claim 1 , wherein:
the at least one initiator compound of the mixture includes a Lewis acid coinitiator and an initiator selected from the group consisting of: a) organic ethers, b) organic esters, c) organic alcohols, d) organic halides, including tert-ester, tert-ether, tert-hydroxyl and tert-halogen containing compounds, e) alkyl cumyl ethers, cumyl halides, alkyl cumyl esters, cumyl hydroxyl compounds and hindered versions of the same, f) dicumyl chloride, g) 5-tert-butyl-1,3-bis(1-methoxy-1-methylethyl)benzene (HDCE), h) initiators having three or more initiation sites, and i) tricumyl chloride.
6. A method according to claim 1 , wherein:
the at least one initiator compound of the mixture includes a Lewis acid and 5-tert-butyl-1,3-bis(1-methoxy-1-methylethyl)benzene (HDCE).
7. A method according to claim 1 , wherein:
the at least one olefin monomer having a pendant BCB group comprises a monomer having the formula
wherein R is hydrogen or an alkyl group and n is 0.
8. A method according to claim 7 , wherein:
the at least one olefin monomer having a pendant BCB group comprises 4-vinylbenzocyclobutene or 2-(4-benzocyclobutenyl)-propene.
9. A method according to claim 1 , wherein:
the at least one olefin monomer having a pendant BCB group comprises a monomer having the formula
wherein R is alkyl group and n is an integer ranging from 0-3.
10. A method according to claim 9 , wherein:
the at least one olefin monomer having a pendant BCB group comprises 2-methyl-3-(4-benzocyclobutenyl)-propene.
11. A method according to claim 1 , wherein:
the copolymer further includes a glass-forming monomer selected from the group consisting of styrene, indene, α-methylstyrene, p-tert-butylstyrene, p-chlorostyrene, norbornene, and combinations thereof.
12. A method according to claim 11 , wherein:
the glass-forming monomer is styrene.
13. A method according to claim 1 , wherein:
the at least one olefin monomer having a pendant BCB group is present in amount ranging from 0.01 to 60 mol % of the monomeric units of the copolymer.
14. A method according to claim 1 , wherein:
the carbocationic polymerization reaction is a living cationic polymerization reaction.
15. A method according to claim 1 , wherein:
the copolymer undergoes crosslinking when exposed to temperatures of at least 180° C.
16. A method of preparing a thermoset polymer comprising:
processing a copolymer prepared according to claim 1 to form a resultant thermoset polymer, wherein the processing includes heating the copolymer such that the copolymer undergoes crosslinking to form the resultant thermoset polymer.
17. A method of preparing an implantable medical device comprising:
processing a copolymer prepared according to claim 1 to form at least part of the implantable medical device, wherein the processing includes heating the copolymer such that the copolymer undergoes crosslinking to form a resultant thermoset polymer that is part of the implantable medical device.
18. A method according to claim 17 , wherein:
the implantable medical device comprises an intraocular lens.