The present invention includes compositions suitable for air barriers such
as innerliners where adhesion to tire carcass materials (e.g., SBR) and
flexibility are desirable, as well as low air permeability. The invention
includes a tire innerliner made by combining a filler; a sulfur cure
system; optionally at least one secondary rubber; and at least one
halogenated terpolymer of C.sub.4 to C.sub.8 isoolefin derived units,
C.sub.4 to C.sub.14 multiolefin derived units, and p-alkylstyrene derived
units. Examples of suitable fillers include modified carbon black, carbon
black, silica, exfoliated clays, and combinations thereof. The present
invention also includes a method of producing an elastomeric terpolymer
composition comprising combining in a diluent C.sub.4 to C.sub.8
isoolefin monomers, C.sub.4 to C.sub.14 multiolefin monomers, and
p-alkylstyrene monomers in the presence of a Lewis acid and at least one
initiator to produce the terpolymer. Examples of suitable initiators
include cumyl compounds and or halogenated organic compounds, especially
secondary or tertiary halogenated compounds such as, for example,
t-butylchloride, 2-acetyl-2-phenylpropane (cumyl acetate),
2-methoxy-2-phenyl propane (cumylmethyl-ether),
1,4-di(2-methoxy-2-propyl)benzene (di(cumylmethyl ether)); the cumyl
halides, particularly the chlorides, such as, for example
2-chloro-2-phenylpropane, cumyl chloride
(1-chloro-1-methylethyl)benzene), 1,4-di(2-chloro-2-propyl)benzene
(di(cumylchloride)), and 1,3,5-tri(2-chloro-2-propyl)benzene
(tri(cumylchloride)); the aliphatic halides, particularly the chlorides,
such as, for example, 2-chloro-2,4,4-trimethylpentane (TMPCl), and
2-bromo-2,4,4-trimethylpentane (TMPBr).