Potentially biodegradable polymers based on α- or β-pinene and sugar derivatives or styrene, obtained under normal conditions and on microwave irradiation

Article abstract of DOI:10.1002/ejoc.200600890

The homopolymerisation of α- and β-pinene and their copolymerisation with styrene and hepta-O-benzyl-6′-O-methacryloyl-sucrose (BMS) have been examined in the presence of AIBN as free-radical initiator, either in toluene or without solvent at 80°C at normal pressure and also in a synthetic microwave oven. A study of the effect of the reaction conditions, the monomer structure and the initial ratio of the comonomers on the properties of the final copolymers, each containing two natural products, has been carried out. A new procedure for synthesising poly(β-pinene), poly(α-pinene- co-styrene), and poly(β-pinene-co-styrene) in short reaction times and under mild conditions with microwave irradiation was found. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejoc.200600890

FULL PAPER
DOI: 10.1002/ejoc.200600890
Potentially Biodegradable Polymers Based on α- or β-Pinene and Sugar
Derivatives or Styrene, Obtained under Normal Conditions and on Microwave
Irradiation
Maria Teresa Barros,*[a] Krasimira T. Petrova,*[a] and Ana Maria Ramos[a]
Keywords: Green chemistry / Pinene / Sucrose / Biodegradable copolymers / Radical copolymerisation / Microwave irradia-
tion
The homopolymerisation of α- and β-pinene and their copoly-
merisation with styrene and hepta-O-benzyl-6Ј-O-methacryl-
oyl-sucrose (BMS) have been examined in the presence of
AIBN as free-radical initiator, either in toluene or without sol-
vent at 80 °C at normal pressure and also in a synthetic mi-
crowave oven. A study of the effect of the reaction condi-
tions, the monomer structure and the initial ratio of the co-
monomers on the properties of the final copolymers, each
containing two natural products, has been carried out. A new
procedure for synthesising poly(β-pinene), poly(α-pinene-co-
styrene), and poly(β-pinene-co-styrene) in short reaction
times and under mild conditions with microwave irradiation
was found.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
change resins,[14] with methyl methacrylate[15] – have been
reported. To the best of our knowledge, though, there are
no reports on copolymers of pinene with sugar-derived
monomers.
1. Introduction
The main constituents of pine resin distillate are α- and
β-pinene, representing a significant source of economically
important raw materials. Development of novel applica-
tions for these abundant and renewable biomass feedstocks
would add to their value.[1]
There are very few reports on the radical polymerisation
of pinenes. The first dates from 1959, when Rozhkov re-
ported the free radical copolymerisation of terpenes with
methyl methacrylate[16] and acrylonitrile[17] in the presence
of AIBN, whilst a British patent from 1964 deals with the
same topic.[18] There followed other works by the same au-
thors on the radical copolymerisation of limonene, but not
of α-and β-pinene.[19,20] A free radical copolymerisation of
α-pinene with acrylonitrile with benzoyl peroxide as cata-
lyst[21] has been reported, as have a synthesis of graft co-
polymers of β-pinene with methyl methacrylate and butyl
acrylate by a combination of living cationic and atom trans-
fer radical polymerisation,[15] and copolymerisation with
maleic anhydride using AIBN.[13] Kinetic studies of the free
radical homo- and copolymerisation of α-and β-pinenes
with styrene and methyl methacrylate with AIBN as an ini-
tiator have been carried out.[22,23]
Commercial polymers of these compounds have the com-
mon name “terpenic resins” and are normally obtained by
Lewis acid-catalysed polymerisation. The most useful ter-
penes for production of these resins are β-pinene, dipentene,
and α-pinene.[2] They have relatively low molecular weights
and afford linear thermoplastic resins with light colours
and weak mechanical properties, but show increased sta-
bility towards heat and UV irradiation. They find various
applications as tackifying resins and additives in plastic
compositions useful as adhesives,[3,4] electroconductive
parts, thermoplastic mouldings etc.[5] Such compositions
are used for drug-delivery and active compound release sys-
tems,[6,7] as well for other medicinal purposes.[8] The homo-
polymers of α- and β-pinene are also reported to have pesti-
cidal properties (Wilt–Pruf Products, Inc.).
Microwave irradiation has recently proved to be effective
as an alternative to conventional heating for reactions with
compounds that are sensitive and/or have low reactivity.[24]
The energy is applied to the sample homogeneously, which
in many cases allows the reactions to be performed in the
absence of solvent, resulting in more efficient, more econ-
omic, and cleaner chemistry.[25] Monomodal microwave
equipment has overcome the uncertainties associated with
domestic microwave ovens. After fast acceptance in inor-
ganic and organic syntheses, polymer chemists have also re-
Many types of copolymers – including styrene with α-
and β-pinene,[9–11] xylene with β-pinene,[12] maleic anhy-
dride with β-pinene,[13] furfural with α-pinene for ion-ex-
[a] REQUIMTE, CQFB, Departamento de Química, Faculdade de
Ciências e Tecnologia, Universidade Nova de Lisboa,
2829-516 Caparica, Portugal
Fax: +351-212948550
E-mail: mtbarros@dq.fct.unl.pt
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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FULL PAPER
cently discovered this new kind of microwave reactor, and synthesis of sucrose-containing linear polymers.[36,37]
A
the growing interest in the use of microwave irradiation for route to selective derivatisation of the 6Ј-position of the su-
polymerisations is reflected in an almost exponential in- crose, developed in our laboratory,[38,39] allowed us to ob-
crease in the number of publications in this field.[26] The tain the fully protected sucrose with only the 6Ј-hydroxy
main applications of microwave polymerisation are in the unprotected, and from this intermediate we prepared unsat-
preparation of dental materials, polymer modification reac- urated sucrose esters (Figure 1).[40] These monomers could
tions, and curing processes.[27] So far, most polymerisations be converted into pure linear polymers.
performed under microwave irradiation conditions have
The homopolymerisation of α-and β-pinene, as well as
been of well investigated monomers such as styrene or their copolymerisation with styrene and the monomer BMS
methyl methacrylate,[28–30] most of them comparing thermal (hepta-O-benzyl-6Ј-O-methacryloyl-sucrose), were exam-
and microwave effects with or without initiator, or search- ined in the presence of AlCl3 as a cationic and AIBN as a
ing for controlled living or atom-transfer systems. To the free-radical initiator, either in toluene or without solvent at
best of our knowledge, there are no reports relating to mi- 80 °C at normal pressure in a focused microwave oven or
crowave-assisted polymerisation of terpenes.
with conventional heating, followed by precipitation in cold
Growing attention[31,32] has recently been paid to the hy- methanol. A study of the effect of the reaction conditions,
pothesis that polymers with interesting biodegradability the monomer structure and the initial quantity of the co-
properties could be available from monomers such as vinyl monomers on the sugar incorporation into the final copoly-
sugars. In this work we have obtained homo- and copoly- mers has been carried out. As a result we obtained a
mers of α- and β-pinene with styrene and sucrose mono- number of copolymers with diverse protected sucrose con-
mers, comparing cationic and free radical polymerisation, tent, with different chain lengths, reported in terms of the
as well as microwave irradiation and conventional heating. weight average molecular weight (Mw), polydispersity (Mw/
In order to incorporate the sucrose moieties into the poly- Mn, Mn being the number average molecular weight), and
mer we opted to attempt a free radical approach, as this with some physical properties such as optical rotations
reaction is slower and more conducive to copolymerisation ([α]D) and glass transition temperatures (Tg).
than cationic polymerisation. As a continuation of our
work on the chemical transformation of sugars,[33–35] we
studied the radical copolymerisation of a vinyl sugar start-
ing material with α- and β-pinene. Copolymers with a wide
range of compositions were synthesised and the influences
of the experimental conditions on reactivity, incorporation
ratios and average molecular mass, as well as some physical
properties, were evaluated.
2.2. Cationic and Radical Homopolymerisation of α- and β-
Pinene
As a first approach to the synthesis of the desired materi-
als, and for intercomparison of the materials, homopoly-
mers of α- and β-pinene, as well as their copolymers with
styrene, were prepared both by cationic polymerisation with
AlCl3 as catalyst and by radical polymerisation with AIBN
under similar conditions. All the samples were characterised
2. Results and Discussion
2.1. Synthesis of Acryl Sucrose Monomer and Its
Application
1
by H NMR and IR. The structures of radical polymers
would be expected to be analogous to the cationic
Since sucrose has eight chemically active hydroxy groups, ones[2,41,42] (Figure 2, Figure 3, Figure 4), as proposed by
regioselective derivatisation is important for the selective Roberts and Day, but to have lower molecular masses. The
Figure 1. Synthesis of hepta-O-benzyl-6Ј-O-methacryloyl-sucrose (BMS). i) TBDPSCl, py, 4-DMAP, room temp., 85%. ii) BnBr/NaH,
DMF, Bu4N+I–, room temp., 80%. iii) TBAF, THF, room temp., 85%. iv) [CH2=C(CH3)CO]2O, CH2Cl2, Et3N, 4-DMAP, room temp.,
73%.
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Polymers Based on α- or β-Pinene and Sugar Derivatives or Styrene
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two pinene isomers follow different polymerisation paths:
The best result was achieved under microwave irradiation
β-pinene gives a polymer with a monocyclic monomer unit conditions at a constant power of 300 W (mild conditions,
and, as shown in Figure 2, the chain grows by alternate iso- the reaction temperature was 54 °C) and with a short reac-
merisation and addition steps, whilst the structure of po- tion time: by cationic polymerisation we obtained poly(β-
ly(α-pinene) is not exactly known, as it represents a more pinene) in high yield and with a molecular mass identical
complex case. Dimer formation occurs to a considerable ex- to that of industrial polymers of this type formed under
tent and the main chain probably consists of two repeating much harsher conditions.[44]
units.[43]
2.3. Radical Copolymerisation of α- and β-Pinene with
Styrene
Figure 2. Cationic polymerisation of β-pinene.
Radical copolymerisation of α-pinene and styrene was
carried out under both “conventional” and microwave irra-
diation conditions with an initial 1:1 mol ratio of the mono-
mers. The incorporation of pinene in poly(α-pinene-co-sty-
rene) (Figure 5, Table S2, Supporting Information) was rel-
atively low, due to the higher reactivity of styrene monomer
under free radical conditions. The copolymers were ob-
tained with higher conversion and higher incorporation of
α-pinene under conventional conditions than under micro-
wave irradiation conditions, probably due to the longer re-
Figure 3. Cationic polymerisation of α-pinene (Ruckel, 1975).
action time, whilst the copolymer obtained under MW con-
ditions had higher molecular mass and a similar polydisper-
sity, but contained mainly styrene units. The [α]D and Tg
values were in a range similar to those of similar copoly-
mers reported in the literature.[23]
Figure 4. Cationic polymerisation of α-pinene (Roberts and Day,
1950).
Under microwave irradiation conditions, two different
procedures for cationic and radical homopolymerisation of
α- and β-pinene were tested. The first procedure involved
working at constant power, with temperature monitoring,
whilst the second entailed working at constant temperature,
maintained by controlling the power. The experiments con-
ducted under microwave irradiation conditions are marked
Figure 5. Radical copolymerisation of α-pinene with styrene.
The free radical copolymerisation of β-pinene with sty-
in all the tables (see Supporting Information, Tables S1–S7) rene was also studied under both conventional and micro-
with the abbreviation “MW” in the column “Reaction con- wave irradiation conditions, with an initial 1:1 mol ratio of
ditions”. As can be seen from Table S1, cationic polymerisa- the monomers. The polymers 1 and 2 (Figure 6, Table S3,
tion (catalyst AlCl3) afforded homopolymers with molecu- Supporting Information) consisted only of polystyrene
1
lar weights similar to those reported in the literature (500– without any incorporation of β-pinene, as indicated by H
3000),[23] in relatively short times (10 min for β-pinene) both NMR, and were not characterised by SEC and DSC analy-
under classical conditions and under microwave irradiation ses. MW irradiation proved to be the only method by which
conditions (Entries 1 and 4), while with AIBN even 96 h to achieve incorporation of β-pinene in the copolymer (En-
were not enough. The general procedure for isolation of the try 4, Table S3) in short reaction times. After 4 h the ob-
obtained polymers from the reaction mixture is by precipi- tained copolymer was a viscous oil and it was not possible
tation through the addition of, in our case, cold MeOH, to isolate it from the reaction mixture by precipitation,
which is miscible with the monomers, the solvent, and the whilst after 5 h a powdery precipitate could be precipitated.
initiator, as well as with by-products (e.g., oligomers). The The resulting copolymer represented a relatively low degree
degree of conversion of the monomers to macromolecules of conversion and incorporation of β-pinene, but had a high
is shown as the weight percent of the obtained solid phase molecular mass, which was consistent with the literature
polymers with regard to the initial monomer mixture.
data.[23]
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formation), heated at 80 °C in oil bath. The initial mol ratio
in all experiments was [sug]/[pin] = 0.1.
From the experiments in the presence of solvent
(Table S4), only oily oligomers consisting mainly of pol-
1
ypinene were isolated, as shown by their H NMR spectra.
As can be seen from the Table, the molecular mass and the
rate of incorporation of sugar did not increase with longer
reaction times, and the results obtained after 12 d reaction
time in solution were the same as those after 5 d.
Figure 6. Radical copolymerisation of β-pinene with styrene.
2.4. Effect of the Reaction Time on Free Radical
Copolymerisations of α- and β-Pinenes with Hepta-O-
benzyl-6Ј-O-methacryloyl-Sucrose
For most of the samples obtained by bulk polymerisation
(Table S5), two polymerised fractions were isolated: (1) a
higher molecular mass powder fraction (marked in the
Tables as powder), and (2) a lower molecular mass resinous-
like fraction (marked as resin). The resinous fraction was in
all cases easily soluble in organic solvents such as CHCl3
or CH2Cl2, whilst the powdery fraction was only partially
soluble in these solvents, and in some cases (Entry 3,
Table S5) it was not possible to dissolve it in CHCl3. It is
likely to be a crosslinked part of the polymer, probably as
a result of the presence of the double bonds in the pinene
units. These samples did not show any thermal phenome-
non during DSC analyses, which confirms a high degree of
crosslinking. Since our studies required linear polymers,
only the molecular masses of the resinous fractions were
measured by SEC analyses. The chromatograms showed bi-
modal distributions with two overlapped distinct peaks,
which means that there are two different polymer types
present: either a mixture of polypinene and poly(pinene-co-
sugar) copolymer, or the two homopolymers – polypinene
and polysugar – blended together. At longer reaction times
we obtained higher yields of the higher molecular mass
fraction, but not greater incorporation of sugar. As ex-
pected, optical rotations were higher in the copolymers with
greater incorporation of the optically active comonomer
(Entries 2 and 3, Table S6, Supporting Information). For
comparison, the optical rotation of the monomer BMS is
[α]D20 = +46.88 (c = 1.23, CHCl3)[35] and that of the polypin-
ene [α]2D0 = –6.02 (c = 1.07, CHCl3) (Table S1).
With these results to hand we next examined free radical
copolymerisations of α- and β-pinenes with hepta-O-ben-
zyl-6Ј-O-methacryloyl-sucrose (Figure 7 and Figure 8). Un-
saturated polyolefin-based materials can easily be vulcan-
ised, resulting in elastomers. Through the incorporation of
polar groups it is possible to eliminate one of the main tech-
nical limitations of polyethylene-based materials: their low
binding ability.
Figure 7. Radical copolymerisation of α-pinene with BMS.
2.5. Effect of the Initial Monomer Ratio on the Free
Radical Copolymerisation of α- and β-Pinenes with Hepta-
O-benzyl-6Ј-O-methacryloyl-Sucrose
The rate of incorporation of the sugar monomer was
studied by variation of the initial sugar/pinenes mol ratio
in the presence of AIBN as free radical initiator and with-
out solvent over the range [BMS]/[pin] = 0.05 to 2
(Tables S6 and S7, Supporting Information). The copoly-
1
mer compositions were determined by H NMR by com-
parison of the peak areas for the methylene and methyl pro-
tons in the pinene monomers with those for the 14 sucrose
Figure 8. Radical copolymerisation of β-pinene with BMS.
A study of copolymerisation reactions as a function of protons.
the reaction time was carried out. The polymerisations were
SEC analysis was not possible for all the product sam-
performed in closed vials without prior degassing and with- ples, due to their poor solubilities in chloroform. None of
out stirring, with AIBN as initiator of the free radical poly- the polymers from samples 2–4, or from powder fractions
merisation in two series: in toluene (Table S4, Supporting 5–9 (Table S6) and the powders 3–10 (Table S7), dissolved
Information) and without solvent (Table S5, Supporting In- readily in chloroform, as the resin fractions did. In an at-
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tempt to dissolve the maximum amount of solid, the sam-
In general, the copolymers with β-pinene showed de-
ples were stirred at room temperature for a total of seven creased monomer conversion with higher incorporation of
days in 5 mL vials, after which the solutions were heated the sugar comonomer (determined by 1H NMR) (Fig-
daily at 40 °C for 4 h for another seven days. Even after this ure 10). This could be explained by the sugar monomer be-
treatment the polymers were still not completely dissolved. ing less reactive in the polymerisation reaction, and also
All the samples were filtered and subjected to size-exclusion containing more functional groups, providing more pos-
chromatography. In the cases of Entries 2, Table S6 and S4, sibilities for chain transfer reactions in the reaction mixture.
Table S7, enough material had dissolved for the analysis.
The relationship between the molecular weights and incor-
None of the samples from Tables S6 and S7 showed any poration of the sugar monomer for β-pinene copolymers
thermal phenomena during the DSC analyses. The DSC ex- also showed a maximum, for copolymer 9, Table S7 with an
periments with samples 2, Table S6, and S4, Table S7, were initial monomer ratio [BMS]/[pin] = 0.1 (Figure 11).
carried out between –50 °C and 70 °C, at a heating rate of
10 °Cmin–1, and no transitions were observed. The DSC
thermograms of samples 3 and 5 (Table S7), were also mea-
sured in the range from 20 °C to 200 °C, at a heating rate
of 10 °Cmin–1, and again nothing was observed. The low
solubility of the copolymer samples, the absence of any Tg
temperature, and also the high molecular mass values of
Entries 2, Table S6, and S4, Table S7, suggested that they
were crosslinked.
The molecular masses of the resin fractions were mea-
sured by Size Exclusion Chromatography (SEC) analysis
and, as in previous series (Table S5), showed bimodal distri-
butions of low molecular weight oligomer mixtures before
the crosslinking occurred. The values of polydispersity ob-
tained for the fractions were all very low, close to 1, indicat- Figure 10. Degree of the monomer conversion vs. mol percent of
incorporation of BMS in poly(BMS-co-β-pinene).
ing that they were highly homogeneous.
The results of experiments (Table S6 and S7) carried out
under different conditions show that under microwave irra-
diation conditions and with lower reaction times the incor-
poration of the sucrose derivative in the copolymer was
higher both for α- and β-pinene – [BMS]/[α-pin] = 0.84 and
[BMS]/[β-pin] = 0.56 – when the initial ratio was 0.1.
Analysis of the experimental data showed that with con-
ventional heating the greatest incorporation of sucrose de-
rivative achieved was 0.19, for both α- and β-pinene (En-
try 5, Table S6 and Entry 8, Table S7) and was achieved by
starting from 2.0 and 0.5, respectively.
The relation between the molecular weights and the in-
corporation of the sugar monomer exhibited a maximum
for copolymer 7, Table S6, with the initial monomer ratio
[BMS]/[pin] = 0.5, which also represented the highest
monomer conversion (Figure 9).
Figure 11. Molecular weights of the copolymers vs. mol percent of
incorporation of BMS in poly(BMS-co-β-pinene).
Figure 9. Molecular weights of the copolymers vs. mol percent of
incorporation of BMS in poly(BMS-co-α-pinene).
Figure 12. Optical rotations of the copolymers vs. mol percent of
incorporation of BMS in poly(BMS-co-β-pinene).
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and the powder polymers were purified by repeated dissolution in
toluene and reprecipitation in cold MeOH and dried under vac-
uum.
Optical rotations were lower in the copolymers with
greater incorporation (determined by 1H NMR) of the
sugar monomer for β-pinene copolymers (Figure 12,
Table S7), but higher for the samples with greater initial
proportions of sugar in α-pinene copolymers (Table S6).
General Procedure for Radical Copolymerisation in Solution under
Conventional Conditions: Copolymerisations of the sucrose deriva-
tive BMS with α- and β-pinene were carried out in dry toluene
solutions (0.1 ) in the presence of AIBN as radical initiator (1%
by weight with respect to the monomer mixture). The solutions
were heated at 80 °C in oil bath for the estimated time (see
Tables S4, S6, S7) and were then allowed to cool to room temp.,
and the product was precipitated by dropping it into a 10-fold
amount of cold MeOH. The white solid was filtered and washed
several times with cold MeOH. When possible (if the product was
easily soluble), the powder polymers were purified by repeated dis-
solution in toluene and reprecipitation in cold MeOH and dried
under vacuum. In the cases in which no solid polymer was ob-
3. Conclusion
In this work the use of α- and β-pinenes as comonomers
for the synthesis of polyolefins containing side chain su-
crose moieties by free radical-chain copolymerisation has
been studied. A new procedure for synthesising poly(β-pi-
nene), poly(α-pinene-co-styrene) and poly(β-pinene-co-sty-
rene) in short reaction times under microwave irradiation
conditions was found. Under these new conditions, it was tained, the unreacted alkene monomers were distilled off under
vacuum to provide a resin-like polymer.
possible to reduce the reaction time from several hours to
10 min for homopolymer formation. MW irradiation
proved to be the only method by which to achieve incorpo-
ration of β-pinene in the copolymer with styrene, with reac-
tion times in the 5 h range, rather than the 7 d previously
reported.[23]
Regioisomerically pure vinyl sugar starting materials, ob-
tained from sucrose by regioselective protection/deprotec-
tion sequences, were copolymerised with terpenic mono-
mers. The characterisation of the polymer samples – the
average molecular mass, as well as some physical properties
of the resulting polymeric materials – permits an assessment
of structural, thermal, mechanical and rheological infor-
mation. Greater incorporation of the sucrose monomer was
achieved under MW irradiation conditions for both α- and
β-pinene. The resulting copolymers were formed exclusively
from easy accessible natural products, and continue our
program of research into the synthesis of polymeric materi-
als from renewable starting materials.
General Procedure for Bulk Radical Copolymerisation under Con-
ventional Conditions: Copolymerisations of the sucrose derivative
BMS or styrene with α- and β-pinene were carried out by mixing
the monomers with AIBN (1% by weight with respect to the mono-
mer mixture). The mixtures were heated at 80 °C in oil bath for the
estimated time (see Tables S2, S3, S5–S7) and were then allowed to
cool to room temp., and the product was precipitated by dropping
it into a 10-fold amount of cold MeOH. The white solid was fil-
tered and washed several times with cold MeOH. When possible
(if the product was easily soluble), the powder polymers were puri-
fied by repeated dissolution in toluene and reprecipitation in cold
MeOH and dried under vacuum. The resin fractions were isolated
by concentrating the filtrates and distilling off the unreacted alkene
monomers under vacuum.
General Procedure for Polymerisation and Copolymerisation in a Fo-
cused Microwave Oven: (The experiments conducted under micro-
wave irradiation conditions are marked in all the tables – see Sup-
porting Information – with the abbreviation “MW” in the column
“Reaction conditions”).
The reactions were performed with a MicroSynth Labstation (Mile-
Stone, USA)[46] in closed vials. To the monomer mixture dissolved
in dry toluene or without solvent was added AIBN (1% by weight
with respect to the monomer mixture) under positive pressure of
dry Ar. The vials were closed and a fibre optic sensor, connected
to the system for automatic temperature control, was inserted in a
reference vial. The desired temperature/potency/time protocol was
programmed to work either at constant power, with temperature
monitoring, or at constant temperature, maintained by controlling
the power. After the estimated time (see Tables S1–S3, S6, S7), the
vials were allowed to cool to room temp. and the product was pre-
cipitated by dropping it into a 10-fold amount of cold MeOH. The
white solid was filtered and washed several times with cold MeOH,
and the powder polymers were purified by repeated dissolution in
toluene and reprecipitation in cold MeOH and dried under vac-
uum. In the cases in which no solid polymer was obtained, the
unreacted alkene monomers were distilled off under vacuum to
provide a resin-like polymer.
4. Experimental Section
Reagents and solvents were purified before use.[45] The sucrose
monomer
1Ј,2,3,3Ј,4,4Ј,6-hepta-O-benzyl-6Ј-O-methacryloyl-su-
crose (BMS) was synthesised as reported.[35] Optical rotations were
measured at 20 °C on an AA-1000 polarimeter (0.5-dm cell). NMR
spectra were recorded at 400 MHz in CDCl3 and are expressed as
chemical shift values (δ) in ppm downfield from TMS. Average mo-
lecular weights were determined with a size exclusion chromatog-
raphy (SEC) apparatus at 30 °C with chloroform as eluent and a
series of three columns (103 Å, 104 Å and 105 Å). The calibration
was performed with monodisperse polystyrene standards. Glass
transition temperatures were measured in the second heating cycle
with a rate of 10 °Cmin–1.
General Procedure for Cationic Homopolymerisation of α- and β-
Pinene:[41] A solution of the appropriate monomer in dry toluene
(0.1 ) was cooled to 0 °C, AlCl3 (5 wt.-%) was added under posi-
tive dry Ar pressure, and the mixture was stirred for an additional
2 h at 50 °C. The catalyst was removed by stirring with HCl (0.1 ,
10 mL/mmol monomer), and the organic phase was washed with
NaOH (0.1 ) and H2O and concentrated under vacuum. The resi-
due was dissolved in toluene and precipitated in cold MeOH, the
white solid was filtered and washed several times with cold MeOH,
Supporting Information (see also the footnote on the first page of
this article): Experimental conditions and analyses results for the
obtained 43 polymer samples, summarised in seven tables with list-
ing for each experiment of the initial mol ratio of the monomers,
the presence/absence and type of solvent, type of catalyst, reaction
temperature (indicating conventional heating or microwave irradia-
tion), reaction time, obtained monomer ratio in the copolymer and
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Polymers Based on α- or β-Pinene and Sugar Derivatives or Styrene
FULL PAPER
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Acknowledgments
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Received: October 10, 2006
Published Online: January 17, 2007
Eur. J. Org. Chem. 2007, 1357–1363
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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