Macromolecules 2003, 36, 2397-2403
2397
Homopolymers and Random Copolymers of
5,6-Benzo-2-methylene-1,3-dioxepane and Methyl Methacrylate:
Structural Characterization Using 1D and 2D NMR
Holger Wick el, Seem a Aga r w a l,* a n d An d r ea s Gr ein er
Philipps-Universita¨t Marburg, Fachbereich Chemie, Institut fu¨r Physikalische Chemie,
Kernchemie und Makromolekulare Chemie und Wissenschaftliches Zentrum fu¨r
Materialwissenschaften, Hans-Meerwein Strasse, D-35032, Marburg, Germany
Received December 19, 2002; Revised Manuscript Received J anuary 21, 2003
ABSTRACT: Complete structural characterization of 5,6-benzo-2-methylene-1,3-dioxepane (BMDO)
monomer and its homopolymer is carried out using 1D and 2D NMR techniques. Copolymers of BMDO
were made with MMA under ATRP reaction conditions. The copolymer compositions were obtained from
1H NMR spectroscopy. The reactivity ratios for the copolymerization of BMDO with MMA were determined
using the Kelen-Tu¨do˜s method and was found to be rBMDO ) 0.53 and rMMA ) 1.96. Compositional and
configurational sequence analysis of copolymers is also done.
In tr od u ction
5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) is an-
other interesting cyclic monomer with an exo-methylene
group. It is expected to give good mechanical properties
besides introducing hydrolytic/biodegradable ester link-
ages in vinyl copolymers. It is reported to give quantita-
tive ROP reaction in the presence of both conventional
(AIBN) and living radical (ethyl R-bromobutyrate/CuBr/
2,2′-bipyridine) initiators giving corresponding poly-
Conventional condensation polymerization and ring-
opening polymerization of cyclic esters like lactones and
lactides are generally used for the synthesis of poly-
esters. But more recently, there is an ever increasing
literature on use of cyclic monomers having an exo-
methylene group as starting material for the synthesis
of polyesters using radical initiators.1-7 This radical
initiated method of synthesis of polyesters has its
fundamental importance in easy introduction of bio-
degradable/hydrolytically unstable ester linkages onto
otherwise nonbiodegradable vinyl polymer backbone.
This can easily be achieved by radical-initiated copoly-
merization of exo-methylene cyclic compounds with
vinyl monomers. Much work has already been done on
homo- and copolymerization of 2-methylene-1,3-dioxo-
lanes (MDL) and its substituted derivatives with vinyl
monomers.1,3-5 Studies with MDL and other exo-meth-
ylene cyclic compounds clearly show that the mecha-
nism of reaction after the initiation step with a radical
varies with the change in the ring size, initiator, and
substituents on the ring. For example, Bailey et al.
showed that 2-methylene-1,3-dioxepane (MDP) (seven-
membered ring) gives quantitative ring-opening poly-
merization reaction to form a polyester in the presence
of radical initiators like azobis(isobutyronitrile) (AIBN)
and di-tert-butyl peroxide (DTBP).5,6 In comparison to
this, five-membered 2-methylene-1,3-dioxolane (MDL)
and six-membered 2-methylene-1,3-dioxane (MDA) gave
both the ester groups by ring-opening polymerization
and acetal groups by vinyl-type addition reactions. But
the presence of phenyl ring as a substituent at the
4-position of MDL (2-methylene-4-phenyl-1,3-dioxolane
(MPDO)) makes the radical-initiated ring-opening
polymerization (ROP) reaction quantitative.6 MPDO
also showed different polymerization behaviors in the
presence of different free radical initiator systems.
Different from its conventional free radical polymeri-
zation, the polymer obtained with living radical initiator
(ethyl R-bromobutyrate/CuBr/2,2′-bipyridine) had both
addition (polyacetal) and ring-opened (polyester) units.8
1
ester. H and 13C NMR techniques are used to charac-
terize the resulting polymer, but the present available
1
literature lacks the complete H NMR characterization,
and also peak assignments to the 13C NMR spectrum
are lacking.9-11 Block copolymerization of BMDO with
methyl acrylate, methyl methacrylate, and styrene by
ATRP is reported by Pan et al.12,13
This paper reports detailed studies on copolymeriza-
tion behavior of BMDO in the presence of methyl
methacrylate (MMA) as comonomer using the benzyl
br om ide/Cu Br /1,1,4,7,7-pen t a m et h yldiet h ylen et r i-
amine ATRP initiating system. To the best of our
knowledge, this is the first attempt to give complete
structural characterization of poly(BMDO) using 1D and
2D NMR techniques. Copolymerization parameters,
stereochemical, and compositional assignments of poly-
(BMDO-co-MMA) are also reported for the first time.
Exp er im en ta l Section
Ma ter ia ls. THF (BASF) was purified by distillation over
potassium. t-Butanol (Aldrich) was dried with calcium hydride,
distilled, and stored under argon. Dimethyl phthalate (Merck),
lithium aluminum hydride (Aldrich), potassium t-butanolate
(Aldrich), hydrochloric acid, (Merck), sulfuric acid (Merck),
1,1,4,7,7-pentamethyldiethylenetriamine (Acros), CuBr (Acros),
p-toluenesulfonic acid (Adrich), and silica gel (Merck) were
used as received. Diethyl ether (BASF), hexane (BASF),
methanol (BASF), and bromoacetaldehyde diethylacetale (Acros)
were distilled before use. Benzyl bromide (Merck) was dried
with Na2SO4 and distilled.
5,6-Benzo-2-methylene-1,3-dioxepane (BMDO) was synthe-
sized in the laboratory using the literature method of Grewe
et al.14 with some modifications (Scheme 1).
Hom o- a n d Cop olym er iza tion of BMDO a n d MMA. In
general, all homo- and copolymerization reactions were carried
out under argon in predried Schlenk tubes under ATRP
* Corresponding author: e-mail seema@chemie.uni-marburg.de.
10.1021/ma025983u CCC: $25.00 © 2003 American Chemical Society
Published on Web 03/13/2003