Mauro Aglietto

Functionalization of montmorillonite by methyl methacrylate polymers containing side-chain ammonium cations

Non-extractable poly(methyl methacrylate) (PMMA)-montmorillonite adducts were prepared by two distinct processes: (a) In the first method, free-radical copolymerization of MMA with clay previously treated with 2-(N-methyl-N,N-diethylammonium iodide) ethyl acrylate (QD1) or 2-(N-butyl-N,N-diethylammonium bromide) ethyl acrylate (QD4) was performed. (b) The second method was based on the direct interaction of montmorillonite with various copolymers of MMA with QD1 or QD4. The structure of the adducts as determined by Fourier-transform infra-red spectroscopy, thermogravimetric analysis and X-ray diffraction was shown to consist of the insertion of MMA macromolecules between lamellar layers whose separation was consequently higher than in the polymer-free clay. The polymer was strongly fixed to the inorganic surfaces, probably due to cooperative formation of electrostatic bonding. The thermal stability of the organic polymers was substantially enhanced in the adducts.

Comparative evaluation of fluorinated and unfluorinated acrylic copolymers as water repellent coating materials for stone

An investigation on the influence of side-chain fluorination on the performance of a series of acrylic-based copolymers as protective coating materials for stones has been carried out by comparing them with unfluorinated polymeric analogues. For this purpose, a series of copolymers of 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDM) and 2,2,2 trifluoroethyl methacrylate (TFEM) with unfluorinated vinyl ether or acrylic comonomers have been synthesized, as well as their not fluorinated analogues, and applied to limestone and marble substrates. A silicone-type commercial product, widely employed in the protection of stones in buildings and other artifacts, has also been tested as a reference material. Their protection efficiencies were then comparatively evaluated in terms of surface properties, water permeability, and appearance. It is shown that the presence of fluorine always has, as expected, a positive influence on the protective action of the polymer, increasing the water repellency of the coated stone.

Some aspects of polypropylene functionalization by free radical reactions

Abstract Hydrocarbon/monomer combination products are detected by GC-MS in the reaction of 2-methylundecane with α-methylstyrene (MES) in the presence of peroxide initiators. On this basis, functionalization experiments of isotactic polypropylene (IPP) and of atactic polypropylene (APP) with MES, diethylfumarate and diethylamaleate have been carried out in solution and in bulk, in the presence of dicumylperoxide. The extent of functionalization, determined by i.r. spectroscopy, depends on the microstructure of the macromolecule being 0.5–1.0% by weight for IPP and 3.0–8.0% by weight for APP. In all functionalization experiments of IPP and APP, partial thermal degradation is observed but crosslinking is negligible.

New fluorinated acrylic polymers for improving weatherability of building stone materials

Acrylic polymers are widely used for their suitability to be shaped in different molecular structures. However, while very appropriate for many applications, these materials are characterized by a limited outdoor stability. In order to improve this last characteristic while maintaining the simple and flexible synthetic route, a study was performed based on the preparation of fluorinated polymers from acrylic monomers where several H-atoms in different positions were replaced with F-atoms. The structure design was aimed to optimize (e.g. minimize) the fluorine content of the final material while obtaining improved chemical and photochemical stability, good filmability and limited permeability to condensed water. The preparation of polymers of methacrylates derived from partially fluorinated alcohol by free radical mechanism is described. The fluorine content and distribution in the macromolecules is modulated by selecting different monomers and by copolymerization with nonfluorinated acrylates or vinylethers. The selection of the comonomers and their relative content in the polymer allows to control the glass transition temperature and the filmability as well as the protection efficiency of the coating. Polymers derived from more complex monomers such as α-trifluoromethyl-methylacrylate are also described. The suitability of these new materials for protective coating of stones is tested by evaluating their stability to different chemical and physical agents and their selective permeability to water vapour vs. condensed water.

Photochemical stability of partially fluorinated acrylic protective coatings. I. Poly(2,2,2-trifluoroethyl methacrylate) and poly(1H, 1H, 2H, 2H-perfluorodecyl methacrylate-co-2-ethylhexyl methacrylate)s

Abstract The photochemical stability and photodegradation pathways of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) and copolymers of 1H,1H,2H,2H-perfluorodecyl methacrylate with 2-ethylhexyl methacrylate (XFDMA–EHMA) have been investigated under artificial solar light irradiation. The extent of degradation was assessed by weight loss and gel content determination, size exclusion chromatography and FTIR spectroscopy. PTFEMA exposed up to 2000 h showed only molecular changes due to a low extent of chain scission. The two XFDMA–EHMA copolymers underwent much more degradation, with extensive cross-linking, formation of low-molecular weight products, and oxidation reactions on the chains. The behaviour of the copolymers is controlled by the reactivity of the EHMA units, as was shown by comparison with results obtained on degradation of PEHMA homopolymer.

Structure control, coating properties and durability of fluorinated acrylic-based polymers

Fluorinated acrylates were employed for the synthesis of conventional, side-chain fluorinated, fully acrylic random copolymers, and of more unusual hybrid copolymers with vinyl ethers. The latter can feature alternating structure and peculiar material properties associated with fluorine or fluorinated groups substitution onto the polymer backbone. Improved efficacy and durability of the resulting coating, highly desirable for the consolidation and protection of highly valued works of art, was achieved through a systematic approach involving a detailed study of their photodegradation behavior, and extensive testing of protection efficacy upon application onto micro-and macroporous stone substrates of different chemical composition and morphology.

Functionalization of SBR copolymer by free radical addition of thiols

The reaction of the random styrene/butadiene copolymer (SBR) with two functional thiols (thioglycolic acid and its aliphatic ester) in the presence of free radical initiators is described. The reaction leads to addition of the thiol group to the vinyl double bonds of the 1,2-butadiene units of the copolymer with high selectivity. As a consequence the resulting macromolecules contain covalently bonded carboxylic or carboxylate groups. The influence of the reaction conditions on the relative probability of the addition reaction with respect to crosslinking, degradation and chain transfer reactions is discussed. The degree of functionalization (FD) can be modulated in the range from 1 to 10 mol-%.

Controlled Functionalization of Olefin/styrene Copolymers through Free Radical Processes

The functionalization of styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) and styrene-co-butadiene (SBR) random copolymer by free radical processes is presented. SEBS was functionalized in the melt with diethyl maleate (DEM) and dicumyl peroxide (DCP) as initiator. The functionalization degree (FD) ranges from 0.1 to 1.6% mol and depends on the feed composition and in particular on the DEM/DCP ratio. Such functionalization takes place with a very large preference at the aliphatic carbons of the polyolefin block. The functionalization of SBR was performed by radical addition in solution of two functional thiols (thioglicolic acid and its aliphatic ester), in the presence of free radical initiators. The addition occurs at the vinyl double bonds of the 1-2 butadiene units with high selectivity. FD can be tuned in the range 1-10mol%. These data are rationalized in the frame of the general reaction mechanism of free radical polymerization. A general reaction scheme is proposed which allows the design of proper conditions for favoring functionalization versus degradation and crosslinking depending on the nature of molecules and macromolecules involved.

Polyolefin functionalization by carbene insertion for polymer blends

Abstract The insertion of controlled amounts of polar ester groups with well defined structure into polyolefin backbones has been accomplished by reacting different polymers with ethyl-(or chloroethyl-)diazoacetate at high temperature (≈ 210° C ). The reaction temperature allowed the polymers to keep in the molten state and complete decomposition of the diazocompound with the formation of carbenic species (:CHCOOC 2 H 5 or :CHCOOC 2 H 4 Cl). The functionalization reaction has been shown to proceed with a one-step mechanism in which the carbene species reacts in the singlet state. Further studies performed with ethylene-propylene copolymers (EPR) allowed optimization of the reaction conditions in order to obtain a rapid and complete decomposition of ethyldiazoacetate and the required (5–10%) low degree of functionalization. Higher degree of functionalization (≈ 10%) is obtained by successive reactions with additional diazoester on the previously functionalized polymer. Infra-red spectra of the functionalized EPR in different solvents indicate that the absorption maxima frequency of the carbonyl band depends on solvent polarity and structure connected to intermolecular interactions of hydrogen-bonding type involving the ester groups of the functionalized polymer and acidic hydrogen present in the solvent.

Photochemical stability of partially fluorinated acrylic protective coatings IV. Copolymers of 2,2,2-trifluoroethyl methacrylate and methyl α-trifluoromethyl acrylate with vinyl ethers

The photochemical stability of copolymers of 2,2,2-trifluoroethyl methacrylate with butyl vinyl ether (TFEMA/BVE) and of methyl α-trifluoromethyl acrylate with 2-ethylhexyl vinyl ether, has been investigated under artificial solar light irradiation. In both copolymers, as well as in a reference ethyl methacrylate/BVE copolymer, the photoageing behaviour is controlled by the reactivity of the corresponding ether component. The degradation occurs mainly in the tertiary positions of the ether units, followed either by formation of γ-lactones or by chain scissions. Only in the case of TFEMA/BVE does the fluorinated methyl of the side chain have an influence on the degradation pathways, i.e. a clear inhibition of cyclization.