1999 рік

The aromatic poly(thioether-ketone) [ArSArCO]n (Ar ˆ 1,4-phenylene) is known to exist in two different crystalline forms, one produced by orientation of the amorphous polymer and the other by heat treatment or crystallisation from the melt. In the present work, single crystal X-ray data for the oligomer [ArCOArSArCOAr] reveal that bond angles at the thioether and carbonyl linkages are substantially different, at 1088 and 1218 respectively, and that the linear chain-conformation required for polymer crystallisation is achieved by a series of bond-angle distortions elsewhere in the molecule—in particular by pyramidalisation of the carbon atoms adjacent to the thioether bridge. Crystal and molecular simulation of orientation-crystallised poly(thioether-ketone) shows that the unit cell is analogous to the “Form II” cell known for poly(etherketone)s. The polymer crystal structure thus has orthorhombic symmetry (two chains per cell), space group Pb2n, a ˆ 4.12, b ˆ 11.30, c ˆ 10.44 Å, and density 1.45 g cm 23. The previously reported monoclinic unit cell is shown to be based on a modification of the present orthorhombic lattice.

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The (AB) n star copolymers (arm number n ¼ 7–77; polyisoprene blocks ¼ ca. 50 vol%) were synthesized by copolymerization of polystyrene (PS)–block–polyisoprene (PI) diblock anions with divinylbenzene (DVB) in benzene. The arm numbers were controlled by changing the initial concentration of the diblock anion or the feed ratio of DVB to the diblock anion end. The microphase-separated structures of (AB) n star copolymers were studied by means of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). It was found that the (AB) n star copolymers composed of symmetric arms (n < 77) formed lamellar structures. The periodic distances of (AB) n star copolymers (n < 77) were the same as those of the corresponding diblock arms.

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The techniques of wide-angle X-ray diffraction, infra-red spectroscopy and differential scanning calorimetry were used to characterize the glass transition and crystallization behavior of freeze-dried isotactic polystyrene (iPS) derived from dilute solutions. It was found that there is a concentration boundary for the original solution: below the boundary, the freeze-dried iPS samples are poorly crystallized but the chains are in a highly ordered 3 1 helix state; above the concentration boundary, the freeze-dried iPS is in a completely disordered amorphous state.

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A new, simplified synthetic route is reported for a novel family of functionalized cyanate monomers. Importantly, the synthetic route has fewer purification requirements, making it a potentially cheaper and more efficient route than previously reported syntheses. The products have been characterized extensively using nuclear magnetic resonance spectroscopy, infrared spectroscopy, and elemental analysis. Bearing alkenyl groups, these materials have the ability to form copolymeric networks with a wide variety of monomers, to yield high performance composite matrices.

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Alternate copoly(amide-imide) was synthesized from two aromatic diamines and trimellitic anhydride (TMA). When the diamine was mphenylenediamine (m-PDA), the resulted poly(amide-imide) [P(A-alt-I)] was found to be of light colour. Specifically, when m-PDA was located between two amide groups in the P(A-alt-I) chain, the P(A-alt-I) was colourless. Using triphenyl phosphite (TPP) and pyridine as condensing agents, a series of P(A-alt-I)s (series III) containing m-PDA was synthesized through direct polycondensation of an aromatic dicarboxylic acid (II b) prepared from m-PDA and TMA, as well as various aromatic diamines. The isomeric series of P(A-alt-I)s (series IV) was synthesized from diacid monomers that had been prepared from various diamines and TMA, as well as m-PDA. The colour (yellow) of P(A-alt-I)s IV was lighter than that of the isomeric series of P(A-alt-I)s III. The 24 P(A-alt-I)s (series III and series IV) had inherent viscosities ranging 1.01–1.88 dl g ¹1. The tensile strengths, elongations to break and initial moduli of the films were 86–112 MPa, 6%–42% and 1.74–2.81 GPa, respectively, and most of the films had yielding. Polymers of Series IV had glass transition temperatures 228°C–293°C, which were higher than those of Series III ranging 223°C–278°C. The 10% weight loss temperatures in nitrogen of these two series were similar in the range 472°C–561°C.

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Segmented poly(ester-urethanes) (PEUs) based on poly(e-caprolactone) (PCL) as a soft segment and a non-aromatic diisocyanate in the hard segment were synthesized. The soft segment crystallinity and other physical properties of the PEUs were studied. It was found that the crystallinity and rate of crystallization of the PCL continuous phase in the PEUs decreases and the glass transition temperature of PEUs increases in comparison with the PCL prepolymers. The restriction of the crystallization of the PCL soft segment depends on the hard segment concentration, length of the soft segment, and total molecular weight of the PEUs.

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The extent of conversion of the reaction between sec-butyllithium and p-divinylbenzene was evaluated by quantitative gas–liquid chromatography. The reaction of stoichiometric amounts of ultra-high purity sec-butyllithium with pure p-divinylbenzene at 08C produces an anionic initiator, 1,4-bis(1-lithio-3-methylpentyl)benzene, 2, in essentially quantitative yields, with low concentrations of monofunctional impurities. Upon the addition of 10 mol% excess of triethylamine to sec-butyllithium, the reaction of sec-butyllithium with p-divinylbenzene at 08C yielded a homogeneous product with composition of 96% difunctionality and 4% monofunctionality, with the total disappearance of p-divinylbenzene as observed by GLC. The high purity 1,4-bis(1-lithio-3-methylpentyl)benzene initiator, 2, is an effective initiator for 1,3-butadiene polymerizations in hydrocarbon solvents and allows the synthesis of polybutadienes with microstructures ranging from 13% to 16% 1,2-vinyl content, as observed by 1 H NMR analysis.

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AKZO NOBEL has developed a new rigid-rod polymer fibre called M5. This new fibre offers high (specific) tensile and compressive mechanical properties, good adhesive bonding with common thermosetting resins, good chemical resistance and a broad useful temperature range up to 600°C. Advanced LightWeight Engineering, in co-operation with the Structures and Materials Laboratory, Faculty of Aerospace Engineering, Delft University of Technology, executes research on composites with this new fibre as reinforcement. The main goals of the research are to establish mechanical properties of M5 composites and to identify attractive applications for M5 composites. This research led to the following conclusions. M5 outclasses most other engineering fibres and its compressive strength must be considered high for a polymeric fibre, with values as high as 1750 MPa derived from three-point bending tests. M5 is suited for use in special products, for which carbon fibres cannot be used, or where the application of M5 offers a significant advantage. Examples of such products are: LPG tanks, drive shafts, Side Impact Protection Beams for cars and Fibre Metal Laminates. M5 can also be used in any other product currently made with carbon fibre composites, except those which exploit the electrical and/or thermal conductivity of carbon fibres.

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A new diamine, 1,1-bis[4-(4-aminophenoxy)phenyl]cyclododecane (BAPCD), bearing flexible ether and bulky pendant cyclododecylidene groups was prepared in three steps from cyclododecanone. The monomer was reacted with six conventional aromatic dianhydrides in N,N-dimethylacetamide (DMAc) to obtain the corresponding new polyimides via the poly(amic acid) precursors and thermal or chemical imidization. The poly(amic acid)s obtained had inherent viscosities ranging from 1.10–1.42 dl g ¹1. All the poly(amic acid)s could be cast from DMAc solutions and thermally converted into transparent, flexible, and tough polyimide films, except for polymer V a which was derived from pyromellitic dianhydride. X-ray diffractograms of polyimides indicated all polymers were amorphous except the polymer V a. Polyimides derived from 4,4⬘-sulfonyldiphthalic anhydride and 4,4⬘-hexafluoroisopropylidenediphathalic anhydride exhibited excellent solubility in various polar solvents. These polymers showed glass transition temperatures between 259°C and 276°C, and decomposition temperatures at initial and 10% mass loss ranging from 430°C to 483°C and from 504°C to 526°C in nitrogen, respectively. The polyimide films, except V a, had a tensile strength in the range 76–112 MPa and a tensile modulus in the range 2.1–3.5 GPa.

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A series of semifluorinated fluorocarbon/hydrocarbon di- and triblock copolymers were prepared by atom transfer radical polymerization (ATRP). The mono- and difunctional macroinitiators, which were obtained from bulk ATRP of styrene, butyl acrylate and methyl acrylate, initiated solution ATRP of 2-[(perfluorononenyl)oxy]ethyl methacrylate and ethylene glycol mono-methacrylate mono-perfluorooctanoate, respectively. The formation of the block copolymer was confirmed with size exclusion chromatography and 1H NMR spectrum.

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