Lewis-acid catalyzed degradation of poly(isobutylene-co-isoprene) (butyl rubber) in the presence of an alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. Simultaneous cleavage and functionalization of butyl rubber was conducted at 270 8C and 240 8C under TiCl 4 or AlCl 3 catalysis in 60/40 hexane/methylene chloride cosolvents in the presence of (3-bromopropoxy)benzene (BPB) for various times up to 24 h. The butyl rubber (EXXON TM Butyl 365) possessed M n 5 1.91 3 10 5 g/mol, PDI 5 1.66 (GPC/MALLS), and 2.30 mol % isoprene units (nearly exclusively trans21,4). At 270 8C with TiCl 4 , molecular weight was reduced to various values within the range 7 to 11 3 10 3 g/mol depending on conditions; lower BPB concentration produced lower molecular weight. However, the ratio of isobutylene repeat units to BPB units (IB/Q) remained constant at about 43:1, which is approximately the same as the ratio of isobutylene to isoprene repeat units (IB/IP) in the starting butyl rubber (42.5:1). At 240 8C with TiCl 4 , molecular weight was reduced to about 5 3 10 3 g/mol, and IB/Q was reduced below IB/IP, indicating nearly a difunctional telechelic structure. AlCl 3 was a more active catalyst and produced results similar to TiCl 4 at 240 8C, even when used at seven times lower concentration.

Abstractexo‐Olefin‐terminated polyisobutylene was obtained directly from living isobutylene polymerizations by addition of a quenching compound to the living chain ends. Three broad classes of compounds were evaluated including hindered bases such as hindered pyridines and piperidines, N‐hydro‐2,5‐disubstitutedpyrroles, and sulfides, ethers, and silylethers. The proposed mechanism of quenching unique to each class was discussed, with supporting kinetic, spectroscopic, and structure‐based evidence presented. Hindered bases were proposed to operate by E2 elimination reaction of free base at the carbenium ion. N‐Hydro‐2,5‐disubstitutedpyrroles were proposed to form the η5‐2,5‐disubstitutedpyrrolyltrichloro‐titanium(IV) coordination complex, which serves as the true quencher. Sulfides, ethers, and silylethers were proposed to operate by first converting the PIB chain ends quantitatively to the onium adduct, which is then decomposed to form exo‐olefin PIB. Sulfides and ethers were the best performing quenchers of all the types studied, particularly bulky ones such di‐tert‐butylsulfide and diisopropyl ether.

The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from their limited rheological tuneability and slow reactions kinetics. The direct ink write (DIW) 3D printing of a two‐part resin, Epon 828 and Jeffamine D230, using a self‐assembly approach is reported. Through the addition of self‐assembling, ureidopyrimidinone‐modified Jeffamine D230 and nanoclay filler, suitable viscoelastic properties are obtained, enabling 3D printing of the epoxy–amine pre‐polymer resin. A significant increase in viscosity is observed, with an infinite shear rate viscosity of approximately two orders of magnitude higher than control resins, in addition to, an increase in yield strength and thixotropic behavior. Printing of simple geometries is demonstrated with parts showing excellent interlayer adhesion, unachievable using control resins.

During living polymerization of isobutylene, marginal conditions can lead to reaction of carbenium ions with exo-olefin and production of coupled polyisobutylene (PIB). When living PIB containing a coupled fraction is subjected to end-quenching with an alkoxybenzene compound in the presence of TiCl4, the coupling reaction is quantitatively reversed to form the two original chain ends, and the regenerated chains are observed to possess the desired alkoxyphenyl functionality. To demonstrate this phenomenon, various PIB samples were prepared to purposefully contain significant coupled fractions, from 10 to 55 mol %, by quenching living PIB with hindered nucleophiles under marginal conditions. The coupled fractions were quantified by 1H NMR and GPC. Coupled PIB samples were reacted with (3-bromo­propoxy)­benzene, methoxy­benzene, or 4-phenoxy-1-butyl acrylate in the presence of TiCl4 and a source of protic catalyst. Various protic sources were found to be effective including externally added water, adventitious protic sources, and any finite fraction of tert-chloride chain ends. Decoupling did not occur in the presence of a proton scavenger such as 2,6-lutidine. The resulting PIB samples were quantitatively or nearly quantitatively decoupled, as determined by 1H NMR and GPC, and all of the chain ends visible by 1H NMR possessed the desired alkoxyphenyl end groups. Other π-nucleophile-type quenchers including N-methylpyrrole, 2-methylfuran, allyltrimethylsilane, and methallyl­trimethylsilane were found to be ineffective under the same or similar conditions due apparently to reaction of the quencher with the necessary protic catalyst.

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