Stereoblock polypropylenes have been obtained performing the polymerization of propene at different temperatures in the presence of [1-methyl-1-naphthylethyl-2-inden-1-yl]zirconium(IV) trichloride and methylaluminoxane. The stereoblock microstructure probably arises from to fact that the zirconium complex exists in equilibrium among structures having the naphthyl group coordinated to the metal, corresponding to chiral and/or pseudo-achiral forms, and a structure having the naphthyl group not coordinated, corresponding to a semimetallocene form. The chiral form produces regular isotactic sequences, whereas the pseudo-achiral and the semimetallocene forms produce atactic sequences, giving rise to isotactic-atactic stereoblocks. The length of the isotactic block depends on the polymerization temperature. A structural characterization and an analysis of the thermal behavior of these stereoblock polypropylenes have been performed. The samples crystallize from the melt in mixtures of R and γ forms of isotactic polypropylene. In the samples polymerized at low temperatures (17 and 30 °C), the amount of γ form is lower than that observed in samples prepared at higher temperatures (50 °C). This indicates that the regular isotactic sequences are longer in samples prepared at low temperatures, according with the interconversion mechanism of the catalyst among isospecific and aspecific forms. In these samples the amount of γ form is, in any case, lower than that observed in the literature for samples having higher stereoregularity and a random distribution of stereodefects, confirming the stereoblock microstructure of the samples prepared with the flexible catalyst.

We recently reported on the synthesis and characterization of CoCl 2 (PRPh 2 ) 2 (R = methyl, ethyl, n-propyl, isopropyl, and cyclohexyl). The catalyst systems obtained by combining the above complexes with methylaluminoxanes (MAO) were highly active in the polymerization of 1,3-dienes, giving 1,2 syndiotactic polymers from butadiene and terminally substituted butadienes (e.g., E-1,3-pentadiene and E-1,3-hexadiene) and 1,2 isotactic polymers from internally substituted 1,3-dienes such as E-3-methyl-1,3pentadiene. We have now polymerized isoprene with the same cobalt catalysts, and unexpectedly the polymers obtained resulted to have an equibinary, alternating cis-1,4/3,4 structure, as indicated by the two-dimensional NMR data. A structure of this type is rather unusual in the field of diolefins stereospecific polymerization, and only few cases have been reported in the literature. An interpretation for the formation of such a polymer is proposed. The structure of cis-1,4-alt-3,4 polyisoprene, with alternating sequences of in-chain and side-chain double bonds, makes it of potential interest in view of a possible selective functionalization of the double bonds.

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Two new polymers envelop a benzothiadiazole dye by π-stacking interactions and a complete FRET is obtained.

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Two novel benzofulvene monomers bearing propargyl or allyl groups have been synthesized by means of readily accessible reactions, and were found to polymerize spontaneously by solvent removal, in the apparent absence of catalysts or initiators, to give the corresponding polybenzofulvene derivatives bearing clickable propargyl or allyl moieties. The clickable propargyl and allyl groups were exploited in appropriate click reactions to develop a powerful and versatile "grafting onto" synthetic methodology for obtaining tailored polymer brushes.

3-Methyl-1,3-pentadiene (mixture of E and Z isomers) was polymerized with the systems CoCl2(PRPh2)2−MAO (R = methyl, ethyl n-propyl, isopropyl, cyclohexyl), obtaining crystalline, essentially isotactic 1,2-poly(E-3-methyl-1,3-pentadiene)s, as indicated by IR and NMR (1H and 13C in solution) analyses. The isotactic content was found to depend on the type of catalyst used (i.e., type of phosphine ligand bonded to the cobalt atom), increasing with decreasing the bulkiness of the phosphine ligand. The same cobalt systems were also used to polymerize 1,3-pentadiene and 1,3-hexadiene, obtaining polymers having the same 1,2 structure, but an opposite tacticity (syndiotactic instead of isotactic). The role played by the monomer structure in determining the polymerization stereoselectivity is discussed.

Two methyl end-capped oligo(ethylene glycol) esters (1a,b) of benzofulvene derivative BF1 were synthesized and induced to polymerize spontaneously by solvent removal to give poly-1a,b showing both NMR and absorption/emission spectra very similar to those of poly-BF1. Poly-1a,b showed relatively high molecular weight and the tendency to depolymerize to a different degree as a function of the temperature in the presence of solvents, while they exhibited appreciable stability in the absence of solvent. Poly-1b, bearing a longer oligo(ethylene glycol) side chain, featured an amphiphilic character and interacted with a number of organic solvents to produce transparent gel aggregates, and with water to give a quite compact physical gel. Rheological studies performed on the hydrogel suggested strong gel characteristics and the combination of rheology and NMR transverse relaxation measurements allowed the pore size distribution in the hydrogel to be defined. Finally, biological studies performed with poly-1b solutions showed neither cytotoxicity nor cell viability impairment suggesting potential biocompatibility features for this polymer. In conclusion, poly-1b can be considered a promising polymer for the preparation of hydrogels potentially useful in a range of biological and biotechnological applications such as drug delivery, molecular recognition, biosensing, protein and DNA separation, micro-and nanofluidics, as well as tissue engineering.