Polysilane spherulites and their high photoluminescence quantum yields

Large polysilane spherulites have been observed. The spherulites were prepared by controlling the removal rate of solvents from poly(n-butyl-n-pentylsilane) under a xylene atmosphere. The diameter of the spherulites was greater than 0.1 mm. The structure of the spherulites was compared with that of the polysilane powder by polarized microscopy, SEM, DSC, and x-ray diffractometry. A high photoluminescence quantum yield of 0.3 was obtained for the spherulites. © 1997 John Wiley & Sons, Inc.     

Spherulites of Tussah Silk Fibroin. Structure, thermal properties and growth rates

The crystal structure, thermal properties and growth rates of spherulites of the Tussah silk fibroin, produced upon drying of the silk taken directly from the lumen which is essentially a poly(L-alanine)polypeptide, are investigated. Depending on casting conditions, spherulites with either αhelical chain conformation or β parallel sheet structure are produced. The growth rates display a strong positive temperature coefficient, with an apparent transition, which however cannot be related with the formation of two different crystal structures at this stage. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and Structure of Butylene Terephthalate-ε-Caprolactone Copolyesters

Butyleneterephthalate-s-caprolactonec0p0lyesters(BCL)are(AB).tYpesegmentedcop0lymersexhibitingatw0-phasestructurewiththeharddomainsasphysicalcr0sslinksf0rrubberysoft-segmentmatrix.Thestructuresofaliphaticandar0maticp0IyesterexistsimultaneouslyinBCLm0lecularchains.Thepr0pertiesofBCLcopoIyestersmayvaryfromth0se0ffragileplastic,t0thermoplasticelastomerandthentohardplasticdependingontheincreaseofhardsegmentc0ntent.Oneofthecomp0nents-poly(E-caprolacton)hasremarkablecompatibi1itywithmanypolyme…     

On the development of special positive isotactic polypropylene spherulites

A new type of positive α‐iPP spherulites has been developed by self‐seeding process. The growth process of these positive α‐iPP spherulites is just like “photographic development process,” which is very different from the conventional growth process of polymer spherulites. Scanning electron microscopy (SEM) was used to explore the morphologies of these positive α‐iPP spherulites on a lamellar level. The results show that these spherulites are composed of a large number of lamellae having interwoven structures, which result in different optical character, special melting behavior, and different contrast under SEM as compared with the conventional melt‐crystallized spherulites. The development of these interwoven lamellar structures has been considered because in the sites of the original spherulites, a large number of self‐nuclei are formed because of the incomplete melting of the original spherulites and these induce nearly equal number of radial and tangential lamellae at rather high temperatures. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1114–1121, 2006     

Chain orientation and distribution in ring‐banded spherulites formed in poly(ester urethane) multiblock copolymer

A poly(ester urethane) multiblock copolymer containing poly(ε‐caprolactone) glycol (PCL) soft segments gives ring‐banded spherulite as crystallized from its melted film. Analysis based on polarized light microscopy and atomic force microcopy revealed that the ring‐banded structures consist of alternate convex and concave bands as a consequence of rhythmic growth. These convex and concave bands, which are composed of flat‐on and edge‐on lamellae, show layered terrace‐like and fibrillar morphology, respectively. The chain orientation and composition distribution in the ring‐banded spherulites were further investigated using FTIR imaging. The convex bands are mainly PCL‐rich domains with perpendicular chain orientation to the substrate, and the concave bands are urethane‐rich domains, where the PCL chains are perpendicular to the radial growth directions of the spherulite but parallel to the film plane. The formation of different orientations in the convex and concave bands is attributed to the rhythmic growth behavior for the copolymers with composition distribution along the chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 541–547, 2010     

Ring‐banded spherulite surface structure of poly(ε‐caprolactone) in its miscible mixtures with poly(styrene‐co‐acrylonitrile)

The surface structure of the ring‐banded spherulites in polymer blends PCL/SAN (90/10) was studied by optical microscopy, SEM, and TEM, respectively. It is interesting to find that the surface structure of the ring‐banded spherulites in polymer blends PCL/SAN (90/10) is made up of the convex bands. The landscape of the convex bands on the surface has been little emphasized before. Radial fibrils are arranged on the bands. Details of the radial fibrils on the bands can be observed by TEM. The landscape of the convex bands on the surface and twisting of lamellae in the convex bands for PCL/SAN blends may be useful to explain the formation mechanism of the ring banded spherulites in polymer blends or even in homopolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2682–2691, 1999     

聚环氧乙烷球晶的带状结构与球晶内部的环形裂纹

聚环氧乙烷球晶的带状结构与球晶内部的环形裂纹丁建东，朱军祥，杨玉良（复旦大学高分子科学系、国家教委聚合物分子工程开放实验室，上海，２００４３３）关键词聚合物，带状球晶，裂纹聚环氧乙烷（ＰＥＯ）具有高度的柔顺性，易于结晶，因而被人们选作研究聚合物结晶的...     

尼龙1010异常光性球晶的旋转观察

通过在偏光显微镜下对尼龙１０１０三类异常光性球晶的旋转观察，发现其消光图案和加一级红补色器时的颜色分布，均随观察角度不同而呈周期性变化，表明其结构单元并并非是沿任一半径均等效排列，而可能是半径不等效的．     

The morphology of poly(vinylidene fluoride) crystallized from blends of poly(vinylidene fluoride) and poly(ethyl acrylate)

A combined optical and electron microscopical study has been carried out of the crystallization habits of poly(vinylidene fluoride) (PVF₂) when it is crystallized from blends with noncrystallizable poly(ethyl acrylate) (PEA). The PVF₂/PEA weight ratios were 0.5/99.5,5/95, and 15/85. Isothermal crystallization upon cooling the blends from the single-phase liquid region was carried out in the range 135–155°C, in which the polymer crystallizes in the α-orthorhombic unit cell form. The 0.5/99.5 blend yielded multilayered and planar lamellar crystals. The lamellae formed at low undercoolings were lozenge shaped and bounded laterally by {110} faces. This habit is prototypical of the dendritic lateral habits exhibited by the crystals grown from the same blend at high undercoolings as well as by the constituent lamellae in the incipient spherulitic aggregates and banded spherulites that formed from the 5/95 and the 15/85 blends, respectively. In contrast with the planar crystals grown from the 0.5/99.5 blend, the formation of the aggregates grown from the 5/95 blend is governed by a conformationally complex motif of dendritic lamellar growth and proliferation. The development of these aggregates is characterized by the twisting of the orientation of lamellae about their preferential b-axis direction of growth, coupled with a fan-like splaying or spreading of lamellae about that axis. The radial growth in the banded spherulites formed from the 15/85 blend is governed by a radially periodic repetition of a similar lamellar twisting/fan-like spreading growth motif whose recurrence corresponds to the extinction band spacing. This motif differs in its fan-like splaying component from banding due to just a helicoidal twisting of lamellae about the radial direction. © 1993 John Wiley & Sons, Inc.     

Transcrystallinity effects in thin polymer films. Experimental and theoretical approach

An experimental and theoretical investigation of the overall crystallization kinetics of thin polymer films containing transcrystalline regions on their surfaces is presented. DSC experiments on polyamide 6-6 show that typical features of crystallization curves can be associated with the occurrence of transcrystallinity. In order to interpret these experimental results, a theoretical model is built within the frame of overall crystallization kinetics theories. It makes it possible to correlate the thickness of transcrystalline zone both to the crystallization temperature, the shape of the peak and the density of nuclei within the polymer. Computer simulation is also used to describe the different steps of structure development within a thin film containing transcrystalline regions.Dedicated to Prof. H. Janeschitz-Kriegl, Linz University, on the occasion of his 70th birthday