Geometrical limits to order in liquid crystalline random copolymers

Hanna, Simon; Windle, A. H.

doi:10.1016/0032-3861(88)90324-2

Cited by 152 publications

(103 citation statements)

References 24 publications

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“…The size, volume fraction and degree of internal perfection of the NPL crystallites will increase if the constituent molecules have additional time to migrate parallel to their chain axes, searching for a better overall match with respect to their immediate neighbours. A similar dependence of microstructure on opportunity for chain mobility has been described for synthetic thermotropic random co-polyesters (Hanna & Windle, 1988). The reinforcement of MAS by NPL crystals offers an obvious benefit to the spider, and a useful lesson to fibre processing technology.…”

Section: Tem Analysismentioning

confidence: 53%

“…It is therefore informative to adapt tools originally developed for npl analysis, and apply them to silk. Previous workers (Hanna & Windle, 1988) have developed a modelling program, named DOMINO, that generates parallel molecules of random co-polymer, and determines the statistical distribution of 'crystallite' sizes (in one dimension) that are formed. An incipient crystallite having a length of n monomers is defined as a region where n successive monomers along a given chain are identical to their immediate neighbours in an adjacent chain, but not necessarily along their own chain.…”

Section: Modellingmentioning

confidence: 99%

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Spider major ampullate silk (drag line): smart composite processing based on imperfect crystals

Thiel

Viney

1997

Journal of Microscopy

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SummaryA spider can spin major ampullate silk (drag line) at rates that differ by more than an order of magnitude, and yet obtain consistently reliable tensile properties. Silk samples collected at different rates and stained by infiltration with tin were studied by transmission electron microscopy. The stained microstructures indicate the presence of nonperiodic lattice crystals, the average size of which depends on the silking rate. A simple statistical point model demonstrates that the ordered regions in major ampullate silk can originate from statistical matches between adjacent chains. The minimum size of the ordered regions is dictated by the fixed monomer sequence in the chains and not by processing kinetics. Inductively coupled plasma-mass spectroscopy shows that the concentration of multivalent protein-binding cations in the unstained fibre is significantly reduced at the higher rates of silking, compared with their concentration at the lowest rates. Qualitatively, this result is consistent with the ions being used to maintain the shear sensitivity of silk secretion over the range of processing rates studied.

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Section: Tem Analysismentioning

confidence: 53%

Section: Modellingmentioning

confidence: 99%

Spider major ampullate silk (drag line): smart composite processing based on imperfect crystals

Thiel

Viney

1997

Journal of Microscopy

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“…The three-dimensional order of the HBA/HNA copolymers is still a matter of debate. 23 Windle In this report, we focus on the alternating copolymer of HBA and HNA, poly(HBA-alt-HNA) and co-workers 24,25 have proposed that these materials consist of ''nonperiodic layer'' (NPL) crysas an approximation to the industrially important random copolymer of the same composition. The tallites to explain the WAXS data.…”

Section: Introductionmentioning

confidence: 99%

“…These NPL crystallites arise from the lateral register of simiadvantage to this approach is the ease with which the ideal state of the macroscopic bulk may be lar but nonperiodic sequences of adjacent chains. Simulations on the extent of order 24 and the difdescribed rigorously. A previous attempt 30 to simulate bulk phases of random copolymers at this fraction characteristics 26 of the NPL crystallites have been presented.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo simulations of a liquid crystal copolymer in the solid state

Foulger

1998

J. Polym. Sci. B Polym. Phys.

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The condensed phase of the alternating copolyester of p‐hydroxybenzoic acid (HBA) and 2‐hydroxy‐6‐naphthoic acid (HNA) is investigated by studying the room temperature packing arrangement of the copolymer chains. A molecular modeling methodology is employed with a Monte Carlo sampling of the configurational phase space. Realistic poly(HBA‐alt‐HNA) polymer chains are represented by an explicit atom representation of the HBA/HNA dimers. States are sampled from the NVT ensemble using a sampling scheme consisting of (1) valence and torsional variations, (2) rigid body rotations of the chain about the chain axis, and (3) rigid body translations of the chain. The effect of chain packing on the conformation of chains, as well as the relative intra‐ and intermolecular orientations of aromatic rings, is investigated. Correlation of chain positioning along the chain axis is dominated by aromatic rings maintaining a center‐to‐center plane of registry. These layers of aromatic units pack with a preference for edge‐to‐face orientations in a herringbone‐type pattern and have an intermolecular ring angle between the pairs of aromatic rings in the unit cell that is ca. 68°. The aromatic rings, on average, are rotated 38° out from the b–c plane. The phenylene rings of these copolyesters are less restricted in their relative orientation in comparison to the naphthalene rings. Intramolecular orientational probability density distributions indicate a preference for staggering the successive aromatic rings along the chain, with a staggering angle of ca. 66°. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 727–741, 1998

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“…11 Patterns described in the literature for solution polymerized material vary from nearly 100 % phase I (e.g., ref. 4) to about 20% phase II (e.g., ref. 15).…”

Section: Introductionmentioning

confidence: 99%

Phase I and II crystals of poly(p-oxybenzoate). I. Effects of substrate and melt polymerization conditions

Rybnikář¹,

Sáha²,

Yuan

et al. 1999

J. Polym. Sci. B Polym. Phys.

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Acid and base treatment of glass and mica substrates affects the phase II/I crystal structure ratio of poly(p‐oxybenzoic acid) polymerized by the confined thin film melt polymerization (CTFMP) technique; acid treatment of mica enhances the phase I content, whereas base treatment of glass and mica results in growth of 100% phase II crystals. In bulk melt polymerized samples, without added catalyst, the fraction of phase II increases with increasing polymerization temperature, up to 25–30% above 300 °C; this is suggested to be related to a “PH phase” (pseudo‐hexagonal), consisting of 3 pairs of phase I and II crystals, rotated by 60°, in CTFMP samples annealed above their Tk‐m. The addition of a base to the polymerization system also results in an increase in the phase II content, up to almost 100% in some cases. The effect of the addition of base is tentatively attributed to a change in the alignment of neighboring molecules growing out from the initial nucleus during the simultaneous polymerization (liquid crystal) crystallization. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3520–3531, 1999

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Geometrical limits to order in liquid crystalline random copolymers

Cited by 152 publications

References 24 publications

Spider major ampullate silk (drag line): smart composite processing based on imperfect crystals

Spider major ampullate silk (drag line): smart composite processing based on imperfect crystals

Monte Carlo simulations of a liquid crystal copolymer in the solid state

Phase I and II crystals of poly(p-oxybenzoate). I. Effects of substrate and melt polymerization conditions

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