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Low Surface Energy Films from Fluorinated Acrylic Latex Blends: Role of Particle Compositin and Size
Full text linkProtezione e consolidamento di materiali porosi: l'impiego di prodotti di sintesi per il recupero conservativo di materiali di pregio
No full textFilm-Forming Behavior and Material Properties of Hybrid Nanostructured Films from Water-Borne Mono- and Multifunctional POSS Copolymers
No full textPolymeric hybrid materials have recently attracted great interest due to their advantageous
performance relative to the non-hybrid counterparts. Typical hybrid materials contain a compact
inorganic phase bonded (often covalently) with an organic phase, which may be phase-segregated or
dispersed at a molecular level. Recently, hybrids containing polyhedral oligosilsesquioxanes (POSS)
either covalently bonded to or simply dispersed in the polymer matrix have been the subject of
increasing attention. This is due to the potentially interesting properties associated with the unique
structure of the POSS cage, a nanoparticle with silica-like inorganic core (SiO1.5)n (n = 8, 10, 12) and
an outer shell of covalently bonded hydrocarbon or organofunctional groups. These organophilic
POSS derivatives can be incorporated into virtually any polymer and, depending on the specific
polymer-POSS interaction, provide the polymer matrix with enhanced or new application properties.
Copolymerization of monofunctional or multifunctional POSS derivatives is an effective way of
achieving a good dispersion of the POSS moieties, and a wide variety of synthetic routes have been
proposed, mainly based on solution or melt processing. On the other hand, the synthesis of POSScontaining
copolymers by hetherophasic polymerization has received much less attention.
We had previously described the first example of the synthesis of hybrid POSS-acrylic copolymer
latexes by miniemulsion polymerization.1 In the present investigation the thermal, mechanical and
surface properties of the nanocomposite latex films at increasing POSS loadings have been evaluated.
Semi-IPN structures were also produced by photopolymerization of monomer-swollen latex films as a
means to further investigate the microgel structure and mechanical properties of the material
Nanostructured Hybrid Materials from Aqueous Polymer Dispersions
No full textOrganic-inorganic hybrids with well-defined morphology and structure controlled at the nanometric scale represent a very interesting class of materials both for their use as biomimetic composites and because of their potential use in a wide range of technologically advanced as well as more conventional application fields. Their unique features can be exploited or their role envisaged as components of electronic and optoelectronic devices, in controlled release and bioencapsulation, as active substrates for chromatographic separation and catalysis, as nanofillers for composite films in packaging and coating, in nanowriting and nanolithography, etc.. A synergistic combination or totally new properties with respect to the two components of the hybrid can arise from nanostructuration, achieved by surface modification of nanostructures, self-assembling or simply heterophase dispersion. In fact, owing to the extremely large total surface area associated with the resulting morphologies, the interfacial interactions can deeply modify the bulk properties of each component. A wide range of starting materials and of production processes have been studied in recent years for the controlled synthesis and characterization of hybrid nanostructures, from nanoparticle or lamellar dispersions to mesoporous materials obtained from templating nanoparticle dispersions in a continuous, e.g. ceramic precursor, matrix.
This review is aimed at giving some basic definitions of what is intended as a hybrid (organic-inorganic) material and what are the main synthetic routes available. The various methods for preparing hybrid nanostructures and, among them, inorganic-organic (I-O) or organic-inorganic (O-I) core-shell nanoparticles, are critically analyzed and classified based on the reaction medium (aqueous, non-aqueous), and on the role it plays in directing the final morphology. Particular attention is devoted to aqueous systems and water-borne dispersions which, in addition to being environmentally more acceptable or even a mandatory choice for any future development of large output applications (e.g. in paint, ink and coating industry), can provide the thermodynamic drive for self-assembling of amphiphilics, adsorption onto colloidal particles, or partitioning of the hybrid’s precursors between dispersed nanosized reaction loci, as in emulsion or miniemulsion free-radical polymerization.
While nanoencapsulation and self-assembling processes are already exploited as commercially viable fabrication methods, a newly developed technique based on two-stage sol-gel and free-radical emulsion polymerization is described, which can grant a versatile synthetic approach to hybrid O-I nanoparticles with tailor-made composition of both the organic core and the silica or organosilica shell, and good control on morphology, size and heterophase structure in the 50-500 nm range.
Styrene or acrylate homo- and copolymer core latex particles need be modified with a reactive comonomer, such as trimethoxysilylpropyl methacrylate (TSPMA), to achieve efficient interfacial coupling with the inorganic shell. Accurate control over pH and process conditions is required to avoid latex coagulation or, in case of organic particles with uniform composition, incipient intraparticle crosslinking
Sintesi di copolimeri anfifilici a blocchi con proprieta’ autoassemblanti tramite processo raft in mezzo acquoso
Full text linkMultifunctional Poly(vinyl ethers) by Controlled Cationic Polymerisation in Fluorinated Solvent
No full textThe living nature of the cationic polymerisation
of butyl vinyl ether (BVE) in the fluorinated solvent
1,1,2-trichloro trifluoroethane was studied, using the initiating
system composed of ethyl aluminium dichloride
(EtAlCl2) as the activator and 1-butoxyethyl acetate
(BEA) as the initiator. BVE homopolymerises in a seemingly
living fashion at T f 08C in the presence of 1,4-
dioxane (DO) as a stabilising Lewis base, although the
fluorinated solvent slows down the polymerisation appreciably.
Less than quantitative reinitiation has been
observed when a second BVE feed was added to the living
macrocation at nearly quantitative monomer conversion.
The functional monomers 2-chloroethyl vinyl ether
(CLEVE), 3-cyano-3-ethoxycarbonylpropyl vinyl ether
(CNEVE) and 1H,1H,2H,2H-perfluorodecyl vinyl ether
(XFDVE) were submitted to polymerisation under the
same conditions that allow to achieve a quasi-living BVE
polymerisation. CLEVE gave a homopolymer with relatively
narrow molecular-weight distribution (MWD),
while efficient polymerisation of XFDVE was only
achieved with BF3 etherate as the initiator. Copolymerisation
of the various functional vinyl ethers with BVE takes
place in a more controlled fashion, yielding products with
narrow MWD index (MÐ
w/MÐ
n = 1.2±1.35), at moderate
functional vinyl ether conversions. Block copolymers
could be synthesised from poly(BVE) living macrocations;
these are probably characterised by a hybrid structure,
consisting of a pure BVE block and a second block
of BVE-functional vinyl ether copolymer
Hybrid and Nanocomposite Materials with Controlled Topologies and Unique Properties from Reactive Polymer Latex and Latex Blends
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