Blends of bisphenol-A polycarbonate and acrylic polymers: II. PC/acrylic copolymers as a new route for compatibilization

An acrylic polymer containing acid and anhydride units, referred to as reactive polyglutarimide (RPGI), has been used to react with PC. The reaction has been previously determined as an acidolysis of the carbonate bond which breaks the PC chain in two parts. One of those two parts remains free while the other one is grafted on the acrylic backbone. We have found that the anhydride units could also react with the carbonate bonds. In this case the PC macromolecule would also be broken in two parts, which would, however, both be grafted on the acrylic backbone. The reaction has been performed in solution in order to keep good contact between the reacting units. The influence of temperature and concentration on the grafting ratio has been studied. The best experimental conditions were determined in order to obtain a grafted copolymer where the acrylic backbone only supports, on the average, one PC side chain through acid reaction or two PC chains through anhydride reaction. Indeed, these two types of reactions could not be isolated. The efficiency of this copolymer as emulsifier has been studied in solution cast blends as well as in melt mixed blends. The copolymer strongly affects the microstructure in solution cast blends where films containing 30 wt % of PC have become transparent. However, the dispersed phase size of solvent cast blends could be highly influenced by the casting conditions related to solvent trapping. In melt mixed samples, the copolymer also reduces significantly the dispersed phase size, but no transparent blends have been observed so far. These results were compared with those given in the literature describing the efficiency of a synthesized copolymer which has a more complicated structure. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 735–747, 1997     

φ production in In–In collisions at 158 A GeV

The NA60 experiment has measured muon pair production in In–In collisions at 158 AGeV at the CERN SPS. This paper presents a high statistics measurement of φ→μ μ meson production. Differential spectra, yields, mass and width are measured as a function of centrality and compared to previous measurements in other colliding systems at the same energy. The width of the rapidity distribution is found to be constant as a function of centrality, compatible with previous results. The decay muon polar angle distribution is measured in several reference frames. No evidence of polarization is found as a function of transverse momentum and centrality. The analysis of the p _T spectra shows that the φ has a small radial flow, implying a weak coupling to the medium. The T _eff parameter measured in In–In collisions suggests that the high value observed in Pb–Pb in the kaon channel is difficult to reconcile with radial flow alone. The absolute yield is compared to results in Pb–Pb collisions: though significantly smaller than measured by NA50 in the muon channel, it is found to exceed the NA49 and CERES data in the kaon channel at any centrality. The mass and width are found to be compatible with the PDG values at any centrality and at any p _T : no evidence for in-medium modifications is observed.     

Probing structural integrity of single walled carbon nanotubes by dynamic and static compression

We report on a first study of single walled carbon nanotubes (SWCNTs) after application of dynamic (shock) compression. The experiments were conducted at 19 GPa and 36 GPa in a recovery assembly. For comparison, an experiment at a static pressure of 36 GPa was performed on the material from the same batch in a diamond anvil cell (DAC). After the high pressure treatment the samples were characterized by Raman spectroscopy and transmission electron microscopy (TEM). After exposure to 19 GPa of shock compression the CNT material exhibited substantial structural damage such as CNT wall disruption, opening of the tube along its axis (“unzipping”) and tube shortening (“cutting”). Dynamic compression to 36 GPa resulted in essentially complete CNT destruction whereas at least a fraction of the nanotubes was recovered after 36 GPa of static compression though severely damaged. The results of these shock wave experiments underline the prospect of using SWCNTs as reinforcing units in material WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

A comparative study of POSS as synergists with zinc phosphinates for PET fire retardancy

This paper deals with the fire behaviour of poly (ethylene terephthalate) (PET) filled with Exolit OP950, a zinc phosphinate fire retardant, and three polyhedral oligomeric silsesquioxanes (POSS) having different chemical structures. Regardless of the POSS type, intumescence occurs during combustion, but the insulation properties of the chars produced are different. Best reductions on total heat evolved (THE) and on cumulative CO₂ with no increase in CO emissions are observed when dodecaphenyl POSS is used. This may be related to its thermal degradation pathway, releasing via this process volatile organic species contributing on intumescence and producing an effective protective layer having a foliated structure.     

Nanocomposites from Untreated Clay : A Myth ?

Polyamide 6 and pristine montmorillonite have been melt blended in an extruder and water was injected into the melt in order to produce nanocomposites. The pristine clay was found to be exfoliated and dispersed homogenously in the nanocomposites. A mechanism explaining the formation of such nanocomposites is presented.     

Blends of bisphenol a polycarbonate and acrylic polymers. I. A chemical reaction mechanism

The chemical reaction at high temperature (above 200°C) between PC and PMMA has been very recently highlighted. However, no clear reaction mechanism has been proposed to explain this phenomenon. We suggest a reaction mechanism following two steps. The first step consists of hydrolysis of the ester bonds of the PMMA leading to acid pendant groups. These acids can then either ring close into glutaric anhydride, or acidolyze the carbonate bonds of PC during the second step. At the same time, benzoic acid produced by PC degradation could further react with PMMA or acidolyze the carbonate groups leading to the crosslinking of the system. A satisfactory contact between the reacting units is a key point in the proces. Significant amounts of PC-PMMA copolymer are obtained when the reaction is performed from a miscible system. On the contrary, no reaction occurs during melt mixing. Understanding the process enables us to specify the conditions, in which no chemical reaction takes place. In nonreactive conditions, PC/PMMA blends remain immiscible for several hours at 300°C. The thermodynamic UCST proposed in the literature is just an artifact due to the occurrence of the chemical reaction. © 1995 John Wiley & Sons, Inc.     

Molecular characterization of maleic anhydride-functionalized polypropylene

This work deals with the molecular characterization of maleic anhydride melt-functionalized polypropylene (PP-g-MA). The functionalization mechanism, the nature, the concentration, and the location of grafted anhydride species onto the polypropylene chain are discussed. The polypropylene functionalization was performed using a pre-heated Brabender Plastograph (190°C, 4 min of mixing time). Several concentrations of maleic anhydride and organic peroxide were used for this study. In those experimental conditions, the organic peroxide undergoes an homolytic rupture and carries out a polypropylene tertiary hydrogen abstraction. The resulting macroradical undergoes a β-scission leading to a radical chain end which reacts with maleic anhydride. When a termination reaction occurs at this first step a succinic type anhydride chain end is obtained. However, oligomerization of maleic anhydride is found to occur more frequently leading to poly (maleic anhydride) chain end. Concentration of both anhydride types and minimal length of the grafted poly (maleic anhydride) were determined. A fraction of maleic anhydride does not react with polypropylene or homopolymerize leading to nongrafted poly (maleic anhydride). © 1995 John Wiley & Sons, Inc.     

Supramolecular Organization of Dye Molecules in Zeolite L Channels: Synthesis,Properties, and Composite Materials

Sequential insertion of different dyes into the 1D channels of zeolite L (ZL) leads to supramolecular sandwich structures and allows the formation of sophisticated antenna composites for light harvesting, transport, and trapping. The synthesis and properties of dye molecules, host materials, composites, and composites embedded in polymer matrices, including two‐ and three‐color antenna systems, are described. Perylene diimide (PDI) dyes are an important class of chromophores and are of great interest for the synthesis of artificial antenna systems. They are especially well suited to advancing our understanding of the structure–transport relationship in ZL because their core fits tightly through the 12‐ring channel opening. The substituents at both ends of the PDIs can be varied to a large extent without influencing their electronic absorption and fluorescence spectra. The intercalation/insertion of 17 PDIs, 2 terrylenes, and 1 quaterrylene into ZL are compared and their interactions with the inner surface of the ZL nanochannels discussed. ZL crystals of about 500 nm in size have been used because they meet the criteria that must be respected for the preparation of antenna composites for light harvesting, transport, and trapping. The photostability of dyes is considerably improved by inserting them into the ZL channels because the guests are protected by being confined. Plugging the channel entrances, so that the guests cannot escape into the environment is a prerequisite for achieving long‐term stability of composites embedded in an organic matrix. Successful methods to achieve this goal are described. Finally, the embedding of dye–ZL composites in polymer matrices, while maintaining optical transparency, is reported. These results facilitate the rational design of advanced dye–zeolite composite materials and provide powerful tools for further developing and understanding artificial antenna systems, which are among the most fascinating subjects of current photochemistry and photophysics.     

Melt properties and crystal morphology of polydodecamide plasticized by benzenesulfonamides

The melt of polydodecamide (PA‐12) shows a significant viscosity decrease upon incorporation of benzenesulfonamide plasticizers (BSAs), this effect being maximum for a monofunctional BSA with a 12‐carbon‐atom‐long alkyl chain. Nonexhaustive X‐ray diffraction analysis developed on isothermally crystallized samples validated a two‐phase model for describing PA‐12 plasticized by N‐(n‐butyl)benzenesulfonamide (BBSA). The massive presence of BBSA between the lamellar crystals was established, and lamellar fragmentation was also observed. Further, a steady increase in PA‐12 crystallinity with an increasing BBSA content was evident (and confirmed by DSC) and is consistent with the plasticizer easing the mobility of polymer chains during crystallization. Large melting point depressions resulting from both polymer–plasticizer miscibility and lamellar fragmentation were observed with several mono‐ and bifunctional BSA plasticizers. Phase separation in PA‐12 solid state was only observed at 20 mol % of ?SO₂NH₂, alhough miscibility occurred in the melt. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2022–2034, 2001     

Characterization of novel modified amorphous poly (ether sulphone)s

New high-temperature amorphous polymers with chlorine, amine, and maleimide chain-ends have been synthesized by nucleophilic polycondensation and fully characterized by ¹³C-NMR, ¹H-NMR, and potentiometric titration. From chain-end determination, number average molecular masses were calculated. It was confirmed that transetherification during the synthesis led to a randomized polymer of the monomer residues. For nominally amine-ended polymers obtained by addition of m-aminophenol at the end of the synthesis, a small amount of hydroxyl chain-ends was observed. This is ascribed also to transetherification. Complete reaction of the amine chain-ends with maleic anhydride was demonstrated. Reaction of hydroxyl chain-ends with acetic anhydride was also observed. The thermal stability of these different polymers was investigated; lower thermal stability was observed for amine and maleimide-ended polymers. By two different methods, a T_g around 270d°C was determined for these novel amorphous aromatic polymers. © 1994 John Wiley & Sons, Inc.