Preparation of Well-Compatibilized PP/PC Blends and Foams Thereof

The performance of polypropylene-poly(ethylene brassylate) block and graft copolymers and a polypropylene-polycaprolactone graft copolymer as compatibilizers for polypropylene-rich polypropylene/bisphenol A polycarbonate (PP/PC, 80/20 wt/wt) blends was elucidated. The copolymers were synthesized either by metal-catalyzed ring-opening polymerization or transesterification of a presynthesized polyester, initiated by hydroxyl-functionalized PPs, which themselves were obtained by catalytic routes or reactive extrusion, respectively. Spectroscopic fingerprints of the copolymers from liquid-state nuclear magnetic resonance (NMR) in combination with scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA), and rheology analyses of the blends indicated that the compatibilizers spontaneously organize at the interface of the two immiscible polymers leading to the formation of uniform, stable, nanophase morphologies. The effect of the compatibilizers on the performance of the PP/PC blends was evaluated, and well-compatibilized PP/PC blends showed improved melt strength and strain hardening when compared to pure PP. This was verified by the successful foam extrusion using isobutane as a blowing agent of well-compatibilized PP/PC blends to low-density PP-based foams, for which normally long-chain branched PP is required

Nouveaux Complexes Organométalliques à base de Métaux des Groupes 3 et 13 pour la Polymérisation d'Esters Cycliques

(Jury : C. Darcel, N. Avarvari, M. Etienne, R. Gauvin, C. Thomas , J.-F. Carpentier)Thèse de Doctorat de l'Université de Rennes

Metal-​based catalysts for controlled ring-​opening polymerization of macrolactones : high molecular weight and well-​defined copolymer architectures

This contribution describes our recent results regarding the metal-¿catalyzed ring-¿opening polymn. of pentadecalactone and its copolymn. with e-¿caprolactone involving single-¿site metal complexes based on aluminum, zinc, and calcium. Under the right conditions (i.e., monomer concn., catalyst type, catalyst¿/initiator ratio, reaction time, etc.)¿, high mol. wt. polypentadecalactone with Mn up to 130 000 g mol-¿1 could be obtained. The copolymn. of a mixt. of e-¿caprolactone and pentadecalactone yielded random copolymers. Zinc and calcium-¿catalyzed copolymn. using a sequential feed of pentadecalactone followed by e-¿caprolactone afforded perfect block copolymers. The blocky structure was retained even for prolonged times at 100 °C after full conversion of the monomers, indicating that transesterification is negligible. On the other hand, in the presence of the aluminum catalyst, the initially formed block copolymers gradually randomized as a result of intra- and intermol. transesterification reactions. The formation of homopolymers and copolymers with different architectures has been evidenced by HT-¿SEC chromatog., NMR, DSC and MALDI-¿ToF-¿MS

w-pentandecalactone polymerization and w-pentadecalactone/e-caprolactone copolymerization reactions using organic catalysts

The catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization (ROP) of ¿-pentadecalactone (PDL) and e-caprolactone (CL) has been studied. The polymerization reactions, carried out in bulk monomer and in toluene solution at 100 °C, identified 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with benzyl alcohol (BnOH) as initiator as the only active catalyst for the ring-opening polymerization of PDL and for the copolymerization of PDL and CL. The guanidine N-methyl-TBD (MTBD), 1,2,3-triisopropylguanidine, the amidine 1,8-diazabicycloundec-7-ene (DBU), and other N-heterocyclic organic catalysts such as dialkylaminopyridine (DMAP), imidazole, indoles, and N-heterocyclic carbenes (NHC’s) tested in this study proved to be inactive in the ROP of PDL even for the long reaction times. The polymerization mechanism, kinetic studies, temperature, and monomer concentration effects were investigated both in solution and in bulk monomer. The pseudoliving character of the TBD/BnOH system has been proven by kinetic studies in both toluene solution and bulk monomer. By varying the experimental conditions and the monomer feed composition, highly crystalline poly(PDL-co-CL) random copolymers of various compositions have been prepared using the binary system TBD/ROH as catalyst/initiators. Thermal analysis and 13C NMR spectroscopy show a linear relation of the variation of the random copolymers melting temperatures as a function of comonomer content

w-pentandecalactone polymerization and w-pentadecalactone/e-caprolactone copolymerization reactions using organic catalysts

The catalytic behavior of several inexpensive and simple N-heterocyclic organic catalysts in ring-opening polymerization (ROP) of ¿-pentadecalactone (PDL) and e-caprolactone (CL) has been studied. The polymerization reactions, carried out in bulk monomer and in toluene solution at 100 °C, identified 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) in combination with benzyl alcohol (BnOH) as initiator as the only active catalyst for the ring-opening polymerization of PDL and for the copolymerization of PDL and CL. The guanidine N-methyl-TBD (MTBD), 1,2,3-triisopropylguanidine, the amidine 1,8-diazabicycloundec-7-ene (DBU), and other N-heterocyclic organic catalysts such as dialkylaminopyridine (DMAP), imidazole, indoles, and N-heterocyclic carbenes (NHC’s) tested in this study proved to be inactive in the ROP of PDL even for the long reaction times. The polymerization mechanism, kinetic studies, temperature, and monomer concentration effects were investigated both in solution and in bulk monomer. The pseudoliving character of the TBD/BnOH system has been proven by kinetic studies in both toluene solution and bulk monomer. By varying the experimental conditions and the monomer feed composition, highly crystalline poly(PDL-co-CL) random copolymers of various compositions have been prepared using the binary system TBD/ROH as catalyst/initiators. Thermal analysis and 13C NMR spectroscopy show a linear relation of the variation of the random copolymers melting temperatures as a function of comonomer content

Kinetic investigation on the catalytic ring-opening (Co)Polymerization of (Macro)Lactones using aluminum salen catalysts

The kinetic behavior of the catalytic ring-opening polymerization (cROP) of a range of macrolactones, including ¿-pentadecalaconte (PDL), ambrettolide (Amb), and butylene adipate (BA), and small-ring lactones, including l-lactide (LLA), e-caprolactone (e-CL), e-decalactone (e-DL), and ß-butyrolactone (B-BL), using various aluminum salen complexes was investigated. The cROP rates were shown to be first order both in catalyst and in monomer. The activation energies of the polymerization of PDL and LLA in combination with aluminum salen complexes, with and without tert-butyl groups, were determined, showing that the increase in steric hindrance is negatively affecting the polymerization rate of LLA more than of PDL. Interestingly, an increase of the salen diimine bridge from ethylene to 2,2-dimethyl propylene leads to a dramatic increase in rate for the polymerization of small-ring lactones, while it leaves the rate of polymerization of macrolactones practically unchanged. In order to exploit this difference in reactivity, the synthesis of block-copolymers of e-CL and PDL was attempted using kinetic resolution. However, all the polymers obtained over time were found to be fully random, which appeared to be the result of fast transesterification. Poly(PDL-b-CL) block copolymers were successfully synthesized applying the high reactivity of e-CL in a sequential feed strategy. However, these block copolymers rapidly transform into fully random copolymers as a result of transesterification, which was shown to have a similar rate constant as the rate constant of the polymerization of PDL. By carefully tuning the reaction time polymers with block, gradient or random topology can be obtained

Real System Features and Implications in Underwater Acoustic Networks

As an emerging research area, underwater acoustic network (UAN) has attracted tremendous interests from both academia and industry in recent years. However, little work has been conducted to test algorithms and protocols in real sea experiments. Due to the complexity of acoustic environments and the uncertainties in acoustic systems, it is difficult for theoretical studies or simulations to evaluate UANs in the real world. Studying real system features of UANs has become crucial in the field. In this dissertation, I study the real system features revealed in sea tests and analyze their impact on underwater media access control (MAC), time synchronization and secret key generation protocols. The system features of UANs I identified include the long preamble of acoustic modems, heterogeneous packet delivery, communication range uncertainty, multi-hop interference, and delayed data transmission. Second, I analyze and evaluate representative MAC protocols in sea tests. Based on the field test results, I study the advantages, shortcomings and limitations of different MAC mechanisms and how they work in real systems. I also propose a practical MAC design for UANs. Third, I analyze the temporal and statistical features of message delivery delay in a lab environment and provide some guidelines on practical time synchronization protocol design and performance improvement. Fourth, I evaluate the performance of representative RSS based key generation approaches for underwater secure communications. Meanwhile, solutions to improve the performance in terms of key generation rate, randomness and key agreement probability are provided

Convenient Synthesis of Mono- and Di-β-hydroxy-β-bis(trifluoromethyl)-(di)imines from β-Hydroxy-β-bis(trifluoromethyl)-ketones and (Di)amines

International audienc

Aluminum Complexes of Fluorinated Dialkoxy-Diimino Salen-like Ligands: Syntheses, Structures and Use in Ring-Opening Polymerization of Cyclic Esters

International audienceThe coordination chemistry of new fluorinated dialkoxy-diimino ligands onto Al(III) centers has been studied. Diimino-diols (CF3)2C(OH)CR12C(R2)═N−R3−N═C(R2)CR12C(OH)(CF3)2 ({ONEtNO}H2, R1 = H, R2 = Me, R3 = C2H4; {ONCyNO}H2, R1 = H, R2 = Me, R3 = trans-1,2-cyclohexyl; {MeONEtNO}H2, R1 = Me, R2 = iPr, R3 = C2H4) react selectively with AlMe3, AlMe2Cl, and Al(OiPr)3 to give the corresponding complexes {ONEtNO}AlX (X = Me, 1; Cl, 2; OiPr, 3), {ONCyNO}AlX (X = Me, 5; Cl, 6; OiPr, 7), and {MeONEtNO}AlX (X = Me, 8; Cl, 9) with concomitant alkane or alcohol elimination, respectively. Single-crystal X-ray diffraction studies revealed that complexes 2, 5, 7, 8, and 9 are mononuclear in the solid state with distorted trigonal-bipyramidal to square-pyramidal geometries. Complexes 1−9 were also characterized in CD2Cl2 solution by 1H, 13C, and 19F NMR spectroscopy. Only one symmetric isomer was observed for complexes 1−7, but mixtures of two isomers (one symmetric, one dissymmetric on the NMR time scale) were observed for complexes 8 and 9. The Al-OiPr complexes 3 and 7 are effective initiators for the ring-opening polymerization of ε-caprolactone and racemic lactide, giving polymers with high molecular weights (Mn up to 37 500 g mol−1) and relatively narrow polydispersities (Mw/Mn = 1.08−1.91). The PLAs produced, both under slurry or melt conditions, with either achiral complex 3 or chiral complex 7, have a highly isotactic-enriched stereoblock microstructure (Pmeso = 0.87)