R. Palumbo

Rubber modification of polyamide 6 during caprolactam polymerization: influence of composition and functionalization degree of rubber

Abstract Rubber-modified polyamides 6 (PA 6) were obtained directly during the hydrolytic polymerization of e-caprolactam (CL). An ethylene-propylene elastomer (EPR) and dibutyl succinate grafted EPRs (EPR-g-DBS) were used as rubbery components to yield binary PA 6/EPR-g-DBS and ternary PA 6/EPR-g-DBS blends having about 20% by weight of total rubber. Model reactions and selective extractions of the blends indicated that (EPR-g-DBS)-g-PA 6 copolymers are formed during the CL polymerization. The influence of the grafting degree of EPR-g-DBS and, for ternary blends, of the weight ratio EPR/EPR-g-DBS on the morphology and on the impact properties of the blends was also investigated. A finer and more homogeneous dispersion of rubbery domains has been found for binary blends, while ternary blends exhibit a quasi-bimodal distribution of rubbery domains. The impact properties of ternary blends are enhanced with the increase of the relative amount of functionalized rubber. The dependence of the morphological features and of the impact properties on the functionalization degree is more complex. Straightforward correlations between mode and state of dispersion of rubber domains and impact properties were not found.

Reactivity of π-pentadienyl complexes. Stereochemistry of the addition of amines to the (syn,syn-1,5-dimethylpentadienyl)iron tricarbonyl cation

Abstract Strongly basic amines react with the (syn,syn-1,5-dimethylpentadienyl)iron tricarbonyl cation to give (cis,trans-dienylamine)iron tricarbonyl complexes through an exo attack of the nucleophile on the coordinated pentadienyl group. Weakly basic amines give (trans,trans-dienylamine)iron tricarbonyl complexes, i.e., the reaction proceeds with geometrical inversion. The stereochemistry of the new complexes has been elucidated by NMR, CD and X-ray analysis.

Stereochemistry of the reaction between amines and the pentadienyliron tricarbonyl cation

Abstract The addition of amines to the pentadienyliron tricarbonyl cation gives rise to (cis, trans- or trans, trans-dienylamine)iron tricarbonyl depending on their basicity. The complexes thus obtained can give binuclear species by further reaction with the cation. The stereochemistry of the reaction has been investigated by PMR spectroscopy.

π-Allylpalladium(II) complexes of amino acids

Abstract Novel π-allylpalladium(II) complexes with amino acid anions as bidentate chelating ligands were prerpared, characterized and investigated by means of IR, NMR and X-ra diffraction techniques. Single crystal X-ray analysis of (π-2-methylallyl)(glycinato) palladium(II) has been carried out: Cu-K1 radiation, monoclinic, space group P21/c, a = 12.03(1), b = 12.85(1), c = 10.86(1)», β = 103° 50′(10′), Z = *, The only relevant difference between the two independent molecules in the unit cell was found in the conformation of the glycinato moiety which appears twisted in one molecule and essentially planar in the other.

Synthesis and preliminary characterization of polyesteramides containing enzymatically degradable amide bonds

SummaryMultiblock and regularly alternating biodegradable polyesteramides containing amide bonds susceptible of enzymatic cleavage were prepared and preliminarly characterized by viscosity, IR, 1H-NMR and DSC techniques. L-phenylalanine was used to build up amide linkages containing a phenyl ring adjacent to the acyl group, enzymatically cleavable by chymotrypsin. Monomers having preformed ester groups or biodegradable amide bonds and/or telechelic oligomers of poly(L-lactide) were used as starting materials. Their chain length was regularly increased in order to improve the overall chain flexibility and, hence, to favour the enzymatic attack.

Influence of intra-chain trans double bonds on the melt crystallization of polyamides

Abstract Melt crystallization kinetics of some aliphatic polyamides, with variable amounts of intra-chain double bonds, was investigated by d.s.c. technique. Crystallization isotherms fit the Avrami equation, yielding for the Avrami parameter, n , values independent from the polyamide composition and close to 4. The values of the calorimetric crystallization rate, in the proximity of the melting point, were analysed using the secondary nucleation theory of Hoffman and Lauritzen. The equilibrium melting temperatures, T 0 m , were found to increase regularly with increase in the amount of unsaturation. The free energy of formation of a nucleus of critical dimensions and the surface free energies σ and σ e of the lamellar crystals were determined. The values were correlated with the copolymer composition. Under the same undercooling, an increase in the rate of crystallization with the amount of double bonds in the chain, is observed. This result is related to surface effects; corresponding lowering in the free energy of folding σ e is found.

Synthesis and Characterization of Alternating Polyesteramides

Aliphatic and partially aromatic alternating polyesteramides were prepared from appropriate bisesteramides and aliphatic diols of various chain length. An investigation of their thermal and viscoelastic behaviour showed that the Tm and Tg values of such polyesteramides are those to be expected for a system with intermediate properties between those of the two homopolymers. A discussion of the experimental Tm values in terms of group contributions is presented.

Synthesis and characterization of aliphatic unsaturated polyesters from trans-4-octene-1,8-dioic and trans-3-hexene-1,6-dioic acids

Abstract The influence of the double bond on the thermodynamic parameters, T m , Δ H m and ΔS m of some unsaturated aliphatic polyesters has been found to depend on the number of —CH 2 — groups separating the double bond from the ester linkage. Thus, T m s of the polyesters derived from trans -4-octene-1,8-dioic acid (OD) are lower than those for the corresponding saturated polyesters; no such effect has been observed by comparing T m s of polyesters derived from trans -3-hexene-1,6-dioic acid (HD) and adipic acid respectively. X-ray investigation has shown, for polyesters of the OD series, the presence of the two polymorphic forms.

Effect of intra-chain double bonds on the melt crystallization of aliphatic polyesters

Abstract The influence of intra-chain double bonds on the crystallization rate of a series of linear aliphatic polyesters was investigated. The free energy of formation of a nucleus of critical dimensions decreases with the percentage of double bonds along the chain. The values of the free energy of folding drastically decreases with an almost linear trend with increase in the amount of unsaturation. The results may be interpreted assuming that the increasing chain flexibility decreases the free energy of formation of a nucleus of critical dimensions mainly because of a lamellar surface effect.

Synthesis and physical behavior of polyamide 6,10-poly(butadiene-co-acrylonitrile) segmented block copolymers

Segmented copolymers, characterized by polyamide 6,10 and poly(butadieneco-acrylonitrile) random blocks, were studied. Samples of such copolymers, having different relative content of the two components, were synthesized. Films were prepared by pressure molding and studied using differential scanning calorimetry and dynamicmechanical analysis. Results indicate that a phase segregation occurs and the system can be described by a matrix model. The matrix can be polyamidic or polybutadienic, depending on sample composition, while, in the matrix, the other component is organized in segregated domains.