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54. Functionalized Polyolefins

Author

Aglietto, M., Ruggeri, Giacomo, Luppichini, E., D'Alessio, Aldo, and Benedetti, E.

Published
1993

66. Control of Degradation Reactions during Radical Functionalization of Polypropylene in the Melt

Author

Coiai, S., Passaglia, E., Aglietto, M., and Ciardelli, F.

Abstract

Isotactic polypropylene (iPP) gives very extensive degradation when treated with peroxides above its melting temperature in mechanical mixers or extruders. This undesired reaction is very modestly affected by maleate molecules which on the contrary actively compete with side reactions of macroradicals in the case of ethylene polymers. In this work iPP was treated in a Brabender mixer at 180 °C with peroxide and different selected molecules capable of promptly reacting with the macroradical formed on iPP chain and converting it into a more stable free radical. Furan derivatives, successfully used for iPP cross-linking without any remarkable increase of MFR, were used as free radical removers and maleic anhydride as functionalizing monomer. The results indicate a detectable improvement with respect to the use of maleic monomers and peroxide only, allowing to us get a significant grafting of functional groups and only partial degradation. Moreover, furan derivatives bearing various reactive substituents were used as functionalizing molecules. The results are discussed in the frame of the general mechanism proposed for the free radical functionalization of polyolefin in the melt.

Published
2004

67. Chiral polymer catalysts in preparative organic chemistry: a critical overview

Author

Aglietto, M, Chiellini, E, D'Antone, Salvatore, Ruggeri, Giacomo, and Solaro, Roberto

Subjects
inorganic chemicals, chemistry.chemical_classification, Nucleophilic addition, Double bond, Chemistry, organic chemicals, General Chemical Engineering, General Chemistry, Polymer, Catalysis, Hydrolysis, chemistry.chemical_compound, Nucleophile, Organic chemistry, heterocyclic compounds, Organic synthesis, Solvent effects
Abstract

Object of the present paper is to provide an up-to-date overview in the field of functional chiral polymers as catalysts in preparative organic chemistry. Attention has been in particular limited to "metal-free'' systems, that is, to polymeric systems capable of exerting their own specific the presence of active groups either directly bound to chiral residues or embedded in a chiral environment. This last can be generated by chiral groups located along or within the polymer backbone, sometimes well far apart from the catalytic sites.For convenience the material has been grouped into two major sections dealing with reactions carried out under homogeneous and heterogeneous conditions, respectively. The first section reports on the activity of different catalysts as tested in the hydrolysis of chiral (optically active or racemic) activated esters, whereas in the second section oxidative, reductive, and nucleophilic additions to prochiral activated carbon-carbon or carbon-oxygen double bond have been reported. catalytic role by virtue of

Published
1988
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68. Photochemical Stability of Partially Fluorinated Acrylic Protective Coatings. 2. Copolymers of 1H,1H,2H,2H-Perfluorodecyl Methacrylate with Unfluorinated Acrylic Esters

Author

Lazzari, M., Aglietto, M., Castelvetro, V., and Chiantore, O.

Abstract

The photochemical stability of a series of copolymers of 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDMA) with acrylic or methacrylic unfluorinated esters has been investigated under artificial solar light irradiation. Molecular and chemical changes induced by the light treatment were monitored by weight loss and gel content determination, size exclusion chromatography, and Fourier transform infrared spectroscopy. In XFDMA/methyl acrylate the degradation mainly occurs on the tertiary position of the acrylic units, followed by extensive chain scissions. In the copolymers with butyl acrylate, butyl methacrylate, and lauryl methacrylate, the XFDMA units are not affected by oxidative degradation reaction, and the mechanism of degradation is influenced by the specific reactivity of the unfluorinated comonomer. For these samples the principal degradation effect is the cross-linking of the polymer structure promoted by radicals formed on the alkyl side groups, and it is only partially attenuated by the fluorinated units.

Published
2001

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