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Digitale Medien

Copolymerization of β-pinene with styrene oxide and N-vinylpyrrolidone (1982)

Martínez, Francisco ; Florsheim, René ; Martínez, Héctor

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 20 (1982), S. 1279-1285

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ISSN: 0360-6376

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The copolymerization of β-pinene with styrene oxide (SO) and β-pinene with N-vinylpyrrolidone (VP) was investigated by using SnCl4 in dichloromethane diluent at low temperature. Monomer reactivity ratios were evaluated for both copolymers at -80°C; these are r1(SO) = 2.979 and r2(β-pinene) = 0.002 and r1(VP) = 0.096 and r2(β-pinene) = 0.294.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1982.170200511

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2

Digitale Medien

Influence of tacticity on thermal degradation of PVC. V. Relation between the nature of labile conformations and the polyene distribution in the degraded polymer (1983)

Martinez, G. ; Mijangos, C. ; Millan, J.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 28 (1983), S. 33-43

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Four poly(vinyl chloride) (PVC) samples, 1, 2, 3, and 4, were prepared in bulk using 2,2′-azodiisobutyronitrile at 90°C and 60°C and the same initiator together with UV irradiation at 0°C and -50°C, respectively. Fractions were obtained from samples 2,3, and 4 by extracting with acetone, sample 1 being completely soluble in this solvent. The whole PVC's as well as their acetone soluble and insoluble fractions, were characterized by determining the intrinsic viscosity, the osmometric molecular weight, and the tacticity; then they were thermally degraded up to conversion of 0.3% in powder state. The values of degradation rate for both the insoluble fractions and the whole PVC's were in agreement with some prior results on the influence of syndiotactic sequences on propagation step. The soluble fractions proved to be very unstable in comparison with the insoluble, which, despite the lower molecular weight of the former, seems to obey their higher content of isotactic conformations. The fine polyene distribution in the degraded polymers was carried out by UV-visible spectroscopy. The results reveal the occurrence of two different polyene distributions, and allow for the peculiar one of the soluble fractions to be related to polyenes consisting of two sequences of trans conjugated double bonds separated by a single cis double bond. The results clearly shows that there are two mechanisms for initiation of the PVC degradation, depending on whether it occurs by random unstable structures or by the normal GTTG isotactic or TTTG heterotactic triads. Moreover, these two initiation processes are proved to give rise to different types of polyenes, which accounts for the occurrence of two unlike mechanisms of propagation.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1983.070280104

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3

Digitale Medien

Influence of tacticity on the thermal degradation of PVC. VI. New advances in the degradation process through the behavior of modified PVC samples (1984)

Martínez, G. ; Mijangos, C. ; Millán, J.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 29 (1984), S. 1735-1741

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Three PVC samples having different tacticities, as well as the products resulting from their reaction with sodium thiophenate, which was previously found to occur selectively by some definite isotactic conformations, were degraded at 180°C in solid state up to 0.3%. In agreement with prior works, the stability of the substituted polymers was shown to be higher as the substitution extent increased up to a definite value, which depends on the overall isotactic content of the starting materials. On the other hand, the found changes in polyene distribution for the degraded samples with the substitution extent, as followed by UV-visible spectroscopy, demonstrate that the specific bands at 393, 416, and 437 nm, which are known to be characteristic for the most unstable PVCs, arise from the lability of some chlorine atoms located at GTTG′ (or TTTG) conformations, as prior results suggested. On the basis of the so-obtained correlation between the content of some isotactic triads (especially the GTTG′) and both the thermal instability and the formation of the above-indicated specific polyenes, new advances in the degradation mechanism are proposed.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1984.070290526

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4

Digitale Medien

The effect of the molecular weight on thermal degradation of fractionated PVC (1975)

Millán, J. ; Madruga, E. L. ; Martínez, G.

Weinheim : Wiley-Blackwell

Angewandte Makromolekulare Chemie 46 (1975), S. 81-87

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ISSN: 0003-3146

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Beschreibung / Inhaltsverzeichnis: Ein technisches PVC und eine andere in Substanz bei 40°C hergestellte Probe wurden nach der Lösungsmethode mit Methanol-Cyclohexanon-Gemischen fraktioniert. Beide Polymere geben Fraktionen mit gleicher Taktizität, aber verschiedenen Molekulargewichten. Der thermische Abbau wurde bei 175, 180 und 185°C durch fortlaufende Bestimmung des abgespaltenen HCl in einem Leitfähigkeitsapparat untersucht. Je niedriger das Molekulargewicht ist, desto größer ist die Abbaugeschwindigkeit; dies gilt aber nur für Polymere mit Molekulargewichten bis etwa 60 000 oder 90 000; oberhalb dieser Werte ist die Abbaugeschwindigkeit vom Molekulargewicht unabhängig. Die Spektren der Proben mit dem gleichen Abbauumsatz zeigen, daß die Verteilung der Polyensequenzen gleich ist und daher nicht vom Molekulargewicht beeinflußt wird.

Notizen: A commercial PVC and another one prepared in bulk at 40°C were fractionated by means of fractional solution method using cyclohexanone-methanol mixtures. Both fractionations resulted in two sets of fractions. Their thermal degradation at 175, 180 and 185°C was followed by means of a conductivity cell which allows a continuous titration of the evolved HCl. The results showed that the lower the molecular weight the higher the degradation rate was; nevertheless, this relationship is only valid up to molecular weights of 60 000 to 90 000, from which the degradation rate appeared to be independent on the molecular weight. The UV-visible spectra of the degraded polymers suggest a similar polyene sequence distribution for all the fractions which accounts for a similar mechanism of degradation in contrast to what happens to fractions with different tacticity.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/apmc.1975.050460108

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5

Digitale Medien

The influence of the tacticity on thermal degradation of PVC. III. Verification by ozonization of degraded samples (1979)

Martínez, G. ; Millán, J.

Weinheim : Wiley-Blackwell

Angewandte Makromolekulare Chemie 75 (1979), S. 215-222

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ISSN: 0003-3146

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Beschreibung / Inhaltsverzeichnis: Mit abgebauten PVC-Proben verschiedener Taktizitäten wurden zwei Reihen Ozonolysereaktionen mit 1 und 24 h durchgeführt. Bei der Ozonolyse wurde die Verteilug der Polyensequenzlängen durch UV-Vis-Spektroskopie verfolgt. Die Kettenspaltungszahl der analysierten Proben wurde durch Bestimmung des Molekulargewichtes vor und nach der Ozonolyse berechnet.Die beobachtete Zunahme der kürzeren Polyensequenzen im Vergleich zu längeren Polyensequenzen bei der Ozonolyserektion hängt von den syndiotaktischen Sequenzen ab. Es wurde andererseits gefunden, daß bei PVC die Zahl der Kettenspaltungen nach der vollständigen Ozonolyse um so kleiner ist, je größer der Anteil von taktischen Sequenzen ist.

Notizen: Two sets of ozonization reactions, for 1 h and 24 h respectively, have been carried out at -20°C on degraded samples of PVC having different contents of tactic sequences. The evolution of the polyene sequences distribution with the ozonization was followed by UV-Visible spectroscopy. The number of chain scissions of ozonized samples was calculated from the number average molecular weight measurements before and after ozonization.The observed increase of short polyenes relative to the long polyenes with ozonization was found to depend markedly on the content of syndiotactic sequences. On the other hand, the number of chain scissions after total ozonization was found to be the higher the lower the content of tactic sequences in PVC samples is.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/apmc.1979.050750116

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6

Digitale Medien

The influence of the tacticity on thermal degradation of PVC. II. New results obtained with fractionated polymers (1975)

Millán, J. ; Madruga, E. L. ; Martínez, G.

Weinheim : Wiley-Blackwell

Angewandte Makromolekulare Chemie 45 (1975), S. 177-184

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ISSN: 0003-3146

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Beschreibung / Inhaltsverzeichnis: Bei 40, 0 und -50°C hergestellte PVC-Proben wurden nach verschiedenen Methoden fraktioniert. Die Fraktionen wurden durch Viskositätsmessungen und IR-Spektroskopie charakterisiert. Der thermische Abbau der Fraktionen wurde bei 175, 180 und 185°C durch fortlaufende Messung des abgespaltenen Chlorwasserstoffs in einem Leitfähigkeitsapparat untersucht. Die kinetischen Ergebnisse und die Spektren der Proben zeigen, daß die syndiotaktischen Sequenzen die Ursache für den schnellen Abbau sind und daß dabei lange Polyensequenzen entstehen, wie schon früher bei unfraktionierten Polymeren ermittelt wurde.

Notizen: PVC samples prepared in bulk at 40, 0, and -50°C were fractionated by different methods. The samples were characterized by viscosimetric measurements and by IR spectroscopy in order to determine the tacticity. The thermal degradation of the samples was studied at 175, 180, and 185°C by means of continuous measuring of the evolved HCl in a conductivity apparatus. From the kinetic results and the UV-visible spectra recorded on equally degraded samples follows that syndiotactic sequences give rise to high degradation rates as well as to long polyene sequences in agreement with results previously obtained with unfractionated polymers.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/apmc.1975.050450113

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7

Digitale Medien

Anionic and radical polymerization of p-triphenyl- and p-tributylgermyl-styrenes (1983)

Hirao, Akira ; Shiraishi, Yoshinobu ; Martinez, Francisco ; [weitere]

New York : Wiley-Blackwell

Die Makromolekulare Chemie 184 (1983), S. 961-967

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Anionic polymerization of p-triphenylgermylstyrene (1a) and p-tributylgermylstyrene (1b) were investigated under high vacuum conditions (≈10-6 mbar). Both 1a and 1b were readily polymerized with sodium naphthalide, potassium naphthalide, or α-methylstyrylsodium oligomers to form “living polymers”. The addition of α-methylstyrene to these living systems gave the triblock copolymer, poly(α-methylstyrene-b-p-triphenylgermylstyrene-b-α-methylstyrene). Both monomers were also polymerized radically with AIBN as initiator. Some physical properties of the resulting polymers were examined.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1983.021840508

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8

Digitale Medien

Polyene sequence distribution in modified poly(vinyl chloride) after thermal degradation (1984)

Martinez, Gerardo ; Mijangos, Carmen ; Millan, José-Luis ; [weitere]

New York : Wiley-Blackwell

Die Makromolekulare Chemie 185 (1984), S. 1277-1284

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The products resulting from the reaction of PVC with sodium benzenethiolate were degraded to 0,3% at 180°C in the solid state and at 160°C in solution in trichlorobenzene. The polyene distribution of the polymers after degradation was studied by both UV-visible and resonance Raman spectroscopies, as a function of the degree of substitution. The results show that there are two types of behaviour: that of the PVC sample prior to the substitution reaction together with the samples modified up to a definite degree of substitution which depends on the starting isotactic content, and that of samples with higher degrees of substitution. The former group exhibits not only a steady improvement in thermal stability but also a preferential formation of polyenes of 7 - 9 double bonds whose concentration decreases with increasing degree of substitution. Conversely, for the second group of samples the thermal stability decreases with the degree of substitution and no specific absorption bands are observed. On the basis of earlier work on the selective substitution of the isotactic GTTG and heterotactic TTTG triads during the first stage of the reaction, the present results show that the bands at 393, 416, and 437 nm are related to specific polyenes which result from initiation by the above quoted conformations in PVC, a conclusion for which confirmatory evidence was obtained by resonance Raman spectroscopic examination of the samples. There is, therefore, clear evidence for the occurrence of two distinct degradation mechanisms, one involving initiation by the unstable triad conformations and the other via random initiation at stable and normal structures. To this may be added the initiation by defect structures, which have been extensively documented in the literature.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1984.021850701

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9

Digitale Medien

The cationic polymerization of 2-alkenylfurans, 2Part 1: cf.5. A side reaction leading to polyunsaturated products (1982)

Alvarez, Rubén ; Gandini, Alessandro ; Martínez, Ricardo

New York : Wiley-Blackwell

Die Makromolekulare Chemie 183 (1982), S. 2399-2413

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: A spectroscopic and conductimetric study of the cationic polymerization of 2-vinylfuran (1) and 2-methyl-5-venylfuran (2) showed the existence of an important side reaction originating from a hydride-ion shift from an unsaturated polymer molecule to an active species. The resulting allylic carbocation, in equilibrium with a doubly unsaturated polymer molecule, can react further and the repetition of the mechanism on progressively more conjugated species leads to the formation of a series of highly charge-delocalized carbenium ions absorbing throughout the visible region of the spectrum (and giving high electrical conductivity) and of neutral polyconjugated polymer molecules. Since the hydride-ion abstraction occurs from the tertiary carbon atom of the vinylic chain, vinylidene polymers of monomers such as 2-isopropenylfuran (3) and 2-isopropenyl-5-methylfuran (4) are not susceptible to it. Indeed, their cationic polymerization proceeds without colour formation and conductivity increase.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1982.021831010

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Digitale Medien

The cationic polymerisation of 2-alkenylfurans, 3Part 2: cf. 2.. Spectroscopic study of the alkylation as important side reaction leading to branched products (1983)

Gandini, Alessandro ; Martínez, Ricardo

New York : Wiley-Blackwell

Die Makromolekulare Chemie 184 (1983), S. 1189-1211

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: A spectroscopic (UV, IR, 1H NMR) study of the cationic polymerisation of 2-vinylfuran (1a) and 2-isopropenylfuran (2a) showed the existence of an important alkylation reaction at C5 which competes with normal propagation. The extent of this competition depends on the monomer used and the polymerisation temperature. A comparison of the spectra of standard polymers (prepared by radical or stereospecific polymerisation) with those of polymers obtained by cationic initiation allowed to assess the extent of alkylation and its regiospecificity at C5 2-Methyl-5-vinylfuran (1b) and 2-methyl-5-isopropenylfuran (2b) were found to undergo cationic polymerisation without any interference from alkylation reactions. Reactions between these four monomers and 2-methylfuran in the presence of typical acidic catalysts gave very high yields of alkylated products and no polymerisation, thus confirming the importance of this electrophilic reaction and its possible application to synthetic uses.

Zusätzliches Material: 15 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1983.021840608

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