Abstract:Die unter präparativen Aspekten wichtigste Erkenntnis der Untersu‐chungen ist, daß die Copolymerisation ürber komplexierte Monomere iiber den gesamten Verlauf kontrolliert werden kann, und nicht– wie in der Literatur beschrieben – spontan einsetzt; von grundsltzlich‐ er Bedeutung ist der totale Ausschluß van Oxidationsmitteln (Sauer‐stoff, organische Peroxide) im System bevor die Polymerisation ge‐startet wird. Die Polyreaktion weist viele Merkmale der klassischen, nach einem Radikalkettenmechanismus ablaufend… Show more
“…As has already been demonstrated, the complexation of the acceptor comonomer acrylonitrile (AN) with Lewis acids (i.e., ZnCl 2 ·Et 2 O, EtAlCl 2 ) influences the comonomer reactivities and the copolymerization parameters. ,,, Surprisingly, it was found that bipolymers with periodic comonomer sequences, ideally alternating copolymers of electron donor and acceptor comonomers, can be also synthesized in the presence of strong organic Brönsted acids. ,, This is reflected from the experimental and analytical data of a set of copolymerizations of ethene and acrylonitrile in the presence of different acids carried out at the same reaction conditions (Table , nos. 2−8).…”
Section: Resultsmentioning
confidence: 99%
“…It might be that the microstructure of the polymer chain with regard to the average an−et sequence length and the resulting differences in crystallite size becomes effective, which could be related to the composition of the polymerization mixture and the copolymerization conditions. 7 DSC curves of poly(ethene- alt -acrylonitrile) obtained by free radical copolymerization in the presence of ethylaluminum dichloride in CH 2 Cl 2 at −78 °C (curve 1), of almost strictly alternating ET−AN copolymer obtained by free radical copolymerization at 20 °C in TFA as solvent (mole ratio TFA/AN = 35) (curve 2), and poly(4-cyanotetramethene- stat -acrylonitrile) (curve 3, copolymer composition an/et = 1.25) obtained by free radical polymerization in CH 2 Cl 2 at 40 °C in the presence of TFA (employed mole ratio TFA/AN = 1).…”
Section: Resultsmentioning
confidence: 99%
“…This is clearly demonstrated by the unusual properties of alternating copolymers of acrylics and olefins, such as the semicrystallinity of the alternating copolymers of ethene and acrylic comonomers, e.g. poly(acrylonitrile- alt -ethene), whereas the use of other electron donor monomers leads to amorphous polymers …”
Section: Introductionmentioning
confidence: 99%
“…Unfortunately, most conventional and readily available monomers are not sufficiently electron rich or electron poor to fulfill this condition. The acceptor properties of the electron poor monomer, such as acrylics, can be improved by complexation with Lewis acids, which decreases the electron density of the acceptor monomer, whereby homopolymerization is prevented and the addition of the electron rich donor monomer is accelerated. , This copolymerization has been often described to start spontaneously, but this seems questionable in view of the unequivocally proven free radical initiation. ,− Exceptions might be the copolymerization of complexed acceptor monomers with styrene as electron donor comonomer, for which the initiation by an equimolar donor−acceptor complex between these monomers has been proposed . Furthermore, it was suggested that this copolymerization is governed by the donor and acceptor character of the olefin .…”
The free radical copolymerization of ethene (ET) with
acrylonitrile (AN) in the presence of
carboxylic acids has been studied. Carboxylic acids and
trifluoroacetic acid (TFA) in particular were
found to be useful complexing agents for acrylonitrile with regard to
the alternating copolymerization
with ethene. The complexation via hydrogen bonding could be
observed by IR analysis of the stretching
frequency of the nitrile group in the monomer. The complex
formation resulted in a decrease of the
copolymerization parameter r
1 of the complexed
and the uncomplexed comonomer acrylonitrile, which
was found to decrease with increasing TFA/AN ratio. The degree of
alternation could be increased by
increasing the TFA/AN or the ET/AN ratio in the initial polymerization
mixture. Almost strictly
alternating copolymers were obtained with TFA as solvent. The
copolymers showed high crystallinity
and melting temperatures similar to the strictly alternating copolymer,
which has been synthesized in
the presence of EtAlCl2 as a Lewis acid.
“…As has already been demonstrated, the complexation of the acceptor comonomer acrylonitrile (AN) with Lewis acids (i.e., ZnCl 2 ·Et 2 O, EtAlCl 2 ) influences the comonomer reactivities and the copolymerization parameters. ,,, Surprisingly, it was found that bipolymers with periodic comonomer sequences, ideally alternating copolymers of electron donor and acceptor comonomers, can be also synthesized in the presence of strong organic Brönsted acids. ,, This is reflected from the experimental and analytical data of a set of copolymerizations of ethene and acrylonitrile in the presence of different acids carried out at the same reaction conditions (Table , nos. 2−8).…”
Section: Resultsmentioning
confidence: 99%
“…It might be that the microstructure of the polymer chain with regard to the average an−et sequence length and the resulting differences in crystallite size becomes effective, which could be related to the composition of the polymerization mixture and the copolymerization conditions. 7 DSC curves of poly(ethene- alt -acrylonitrile) obtained by free radical copolymerization in the presence of ethylaluminum dichloride in CH 2 Cl 2 at −78 °C (curve 1), of almost strictly alternating ET−AN copolymer obtained by free radical copolymerization at 20 °C in TFA as solvent (mole ratio TFA/AN = 35) (curve 2), and poly(4-cyanotetramethene- stat -acrylonitrile) (curve 3, copolymer composition an/et = 1.25) obtained by free radical polymerization in CH 2 Cl 2 at 40 °C in the presence of TFA (employed mole ratio TFA/AN = 1).…”
Section: Resultsmentioning
confidence: 99%
“…This is clearly demonstrated by the unusual properties of alternating copolymers of acrylics and olefins, such as the semicrystallinity of the alternating copolymers of ethene and acrylic comonomers, e.g. poly(acrylonitrile- alt -ethene), whereas the use of other electron donor monomers leads to amorphous polymers …”
Section: Introductionmentioning
confidence: 99%
“…Unfortunately, most conventional and readily available monomers are not sufficiently electron rich or electron poor to fulfill this condition. The acceptor properties of the electron poor monomer, such as acrylics, can be improved by complexation with Lewis acids, which decreases the electron density of the acceptor monomer, whereby homopolymerization is prevented and the addition of the electron rich donor monomer is accelerated. , This copolymerization has been often described to start spontaneously, but this seems questionable in view of the unequivocally proven free radical initiation. ,− Exceptions might be the copolymerization of complexed acceptor monomers with styrene as electron donor comonomer, for which the initiation by an equimolar donor−acceptor complex between these monomers has been proposed . Furthermore, it was suggested that this copolymerization is governed by the donor and acceptor character of the olefin .…”
The free radical copolymerization of ethene (ET) with
acrylonitrile (AN) in the presence of
carboxylic acids has been studied. Carboxylic acids and
trifluoroacetic acid (TFA) in particular were
found to be useful complexing agents for acrylonitrile with regard to
the alternating copolymerization
with ethene. The complexation via hydrogen bonding could be
observed by IR analysis of the stretching
frequency of the nitrile group in the monomer. The complex
formation resulted in a decrease of the
copolymerization parameter r
1 of the complexed
and the uncomplexed comonomer acrylonitrile, which
was found to decrease with increasing TFA/AN ratio. The degree of
alternation could be increased by
increasing the TFA/AN or the ET/AN ratio in the initial polymerization
mixture. Almost strictly
alternating copolymers were obtained with TFA as solvent. The
copolymers showed high crystallinity
and melting temperatures similar to the strictly alternating copolymer,
which has been synthesized in
the presence of EtAlCl2 as a Lewis acid.
“…The CH2 = C(Et)-end group is relatively electron-rich. We and other researchers have shown that the electrophilic character of such olefins can be enhanced by the addition of Lewis acids to the reaction mixture [8,9]. The goal of this project was to apply our knowledge and experience in the field of free radical copolymerizations of electron-rich monomers with electrophilic olefins [4,51 to the functionalization of a polyhydrocarbon with a terminal vinyl group.…”
The free radical copolymerization of a vinyl-terminated hydrocarbon macromonomer, namely poly-1-butene with molecular weight 1,000, with methyl acrylate (MA) led to copolymers with broad molecular weight distributions, and even bimodal character. In the presence of alkylaluminum chloride Lewis acids, higher incorporation of MA was obtained. The polymer MW and mole% MA in the copolymer increase with their decreasing Lewis acid strength. The best result was obtained in the presence of 25 mole% Et,AICl versus MA at 60 "C which led to 82% of the polyhydrocarbon chains being derivatized and unimodal MW distribution. For the copolymerization of the polyhydrocarbon macromonomer and AN, the best results were obtained without Lewis acid in toluene using a free radical initiator at 125 "C.The model compound 2,2,4-trimethyl-l-pentene copolymerizes with both MA and AN in standard free radical conditions and the copolymerization parameters were determined.
Acrylonitrile has found its way into a great variety of polymeric compositions based on its polar nature and reactivity. Some of these areas include adhesives and binders, antioxidants, medicines, dyes, electrical insulations, emulsifying agents, graphic arts materials, insecticides, leather, paper, plasticizers, soil‐modifying agents, solvents, surface coatings, textile treatments, viscosity modifiers, azeotropic distillations, artificial organs, lubricants, asphalt additives, water‐soluble polymers, hollow spheres, cross‐linking agents, and catalyst treatments. Styrene–acrylonitrile (SAN) resins possess many physical properties desired for thermoplastic applications. They are characteristically hard, rigid, and dimensionally stable with load bearing capabilities. Modifiers may include uv stabilizers, flow and processing aids, and reinforcing agents. SAN resins show considerable resistance to solvents and are insoluble in carbon tetrachloride, ethyl alcohol, gasoline, and hydrocarbon solvents. Polar solvents such as acetone, chloroform, and pyridine will dissolve SAN. The properties of SAN are significantly altered by water absorption. Commercially, SAN is manufactured by three processes: emulsion, suspension, and continuous bulk. Acrylonitrile copolymerizes readily with many electron‐donor monomers other than styrene. Hundreds of acrylonitrile copolymers have been reported. Copolymers of acrylonitrile and methyl acrylate and terpolymers of acrylonitrile, styrene, and methyl methacrylate are used as barrier polymers. Environmentally degradable polymers are useful in packaging. The largest portion of SAN (80%) is incorporated into ABS resins, and their markets are inexorably joined. SAN resins themselves appear to pose few health problems, and they have been approved by the FDA for food packaging use.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
