Academic literature on the topic 'Microphases. eng'
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Journal articles on the topic "Microphases. eng"
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Zhang, Tao, Guangtao Chang, and Qipeng Guo. "Thermoreversible Polymer Gels in DMF Formed from Charge- and Crystallization-Induced Assembly." Polymers 12, no. 9 (September 10, 2020): 2056. http://dx.doi.org/10.3390/polym12092056.
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Polymer organogels formed through dynamic interactions are interesting for various applications. The fabrication of polymer organogels in polar solvents through ionic interaction is rare, although such organogels in non-polar organic solvents have been well studied. Herein, polymer organogels in a polar solvent N,N-dimethyl formamide (DMF) were fabricated from a triblock copolymer, poly(4-vinyl pyridine)-block-poly(ethylene glycol)-block-poly(4-vinyl pyridine) (4VPm-EGn-4VPm), and a fluorinated surfactant, perfluorooctanoic acid (PFOA), and their microphase separation and properties were studied. Ordered microphase separation and the crystalline structures were revealed by small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS), respectively. All the 4VPm-EGn-4VPm/PFOA organogels are sensitive to temperature, and the ratio of PFOA to pyridine groups reversibly. The polymer organogels are also responsive to triethylamine and triethylammonium acetate.
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German, Ian, Franck D’Agosto, Christophe Boisson, Sylvie Tencé-Girault, and Corinne Soulié-Ziakovic. "Microphase Separation and Crystallization in H-Bonding End-Functionalized Polyethylenes." Macromolecules 48, no. 10 (May 7, 2015): 3257–68. http://dx.doi.org/10.1021/ma502304k.
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Masamoto, J. "Microphase separation in polyoxymethylene end-capped with a long-chain alkyl." Polymer 41, no. 19 (September 2000): 7283–87. http://dx.doi.org/10.1016/s0032-3861(00)00075-6.
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Gavrilov, Alexey A., and Alexander V. Chertovich. "Polymerization-Induced Microphase Separation with Long-Range Order in Melts of Gradient Copolymers." Polymers 12, no. 11 (November 10, 2020): 2637. http://dx.doi.org/10.3390/polym12112637.
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In this work, we studied the question of whether it is possible to develop a one-step approach for the creation of microphase-separated materials with long-range order with the help of spontaneous gradient copolymers, i.e., formed during controlled copolymerization solely due to the large difference in the reactivity ratios. To that end, we studied the polymerization-induced microphase separation in bulk on the example of a monomer pair with realistic parameters based on styrene (S) and vinylpirrolydone (VP) by means of computer simulation. We showed that for experimentally reasonable chain lengths, the structures with long-range order start to appear at the conversion degree as low as 76%; a full phase diagram in coordinates (fraction of VP—conversion degree) was constructed. Rather rich phase behavior was obtained; moreover, at some VP fractions, order–order transitions were observed. Finally, we studied how the conversion degree at which the order–disorder transition occurs changes upon varying the maximum average chain length in the system.
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McLeod, Kelly R., and Gregory N. Tew. "Microphase-Separated Thiol–Ene Conetworks from Telechelic Macromonomers with Asymmetric Molecular Weights." Macromolecules 50, no. 20 (October 9, 2017): 8042–47. http://dx.doi.org/10.1021/acs.macromol.7b01681.
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Nikishau, Pavel A., Evgenii A. Ksendzov, Dmitriy I. Shiman, Ludmila V. Gaponik, and Sergei V. Kostjuk. "Synthesis of functionalized polyisobutylene and its block copolymers with D,L-lactide." Journal of the Belarusian State University. Chemistry, no. 2 (August 30, 2019): 40–50. http://dx.doi.org/10.33581/2520-257x-2019-2-40-50.
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Method of reactive polyisobutylene modification by various alkoxybenzenes (anisole and 4-phenoxybutanol) was proposed to form functionalized polyisobutylenes. Polymerization of D,L-lactide was explored on the 4-phenoxybutanol/1,5,7-triazabicyclo[4.4.0]dec-5-ene system. It led to determination of optimal conditions for gaining of poly(isobutylene-b-D,L-lactide). Such copolymers (Mn = 14 300 g/mol and Mn = 36 600 g/mol, Mw / Mn ≤ 2.5) which were obtained by the polymerization of D,L-lactide on polyisobutylene macroinitiator shows microphase ordering. Formation of the block copolymers is confirmed by 1Н NMR spectroscopy, gel permeation chromatography, and scanning electron microscopy.
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Choi, Taeyi, Jadwiga Weksler, Ajay Padsalgikar, Rebeca Hernéndez, and James Runt. "Polydimethylsiloxane-Based Polyurethanes: Phase-Separated Morphology and In Vitro Oxidative Biostability." Australian Journal of Chemistry 62, no. 8 (2009): 794. http://dx.doi.org/10.1071/ch09096.
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Three series of segmented polyurethane block copolymers were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) or 1,3-bis(4-hydroxybutyl)tetramethyl disiloxane (BHTD) as the hard segments, and soft segments composed of poly(dimethyl siloxane) (PDMS)-based and poly(hexamethylene oxide) (PHMO) macrodiols. Copolymers synthesized with the PDMS macrodiol and PDMS and PHMO macrodiol mixtures consist of three microphases: a PDMS phase, hard domains, and a mixed phase of PHMO (when present), PDMS ether end-group segments and some dissolved hard segments. Degrees of phase separation were characterized using small-angle X-ray scattering by applying a pseudo two-phase model, and the morphology resulting from unlike segment demixing was found to be closely related to the in vitro oxidative biostability of these segmented polyurethanes.
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Chao, Ying-Chieh, Jhe-Han Chen, Yi-Jie Chiou, Po-lin Kao, Jhao-Lin Wu, Chin-Ti Chen, Li-Hsin Chan, and Ru-Jong Jeng. "Design of Thienothiophene-Based Copolymers with Various Side Chain-End Groups for Efficient Polymer Solar Cells." Polymers 12, no. 12 (December 11, 2020): 2964. http://dx.doi.org/10.3390/polym12122964.
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Three two-dimensional donor–acceptor conjugated copolymers consisting of a benzo[1,2-b:4,5-b′]dithiophene derivative and thieno[3,2-b]thiophene with a conjugated side chain were designed and synthesized for use in bulk heterojunction (BHJ) or nonfullerene polymer solar cells (PSCs). Through attaching various acceptor end groups to the conjugated side chain on the thieno[3,2-b]thiophene moiety, the electronic, photophysical, and morphological properties of these copolymers were significantly affected. It was found that the intermolecular charge transfer interactions were enhanced with the increase in the acceptor strength on the thieno[3,2-b]thiophene moiety. Moreover, a better microphase separation was obtained in the copolymer: PC71BM or ITIC blend films when a strong acceptor end group on the thieno[3,2-b]thiophene moiety was used. As a result, BHJ PSCs based on copolymer:PC71BM blend films as active layers exhibited power conversion efficiencies from 2.82% to 4.41%, while those of nonfullerene copolymer:ITIC-based inverted PSCs ranged from 6.09% to 7.25%. These results indicate the side-chain engineering on the end groups of thieno[3,2-b]thiophene unit through a vinyl bridge linkage is an effective way to adjust the photophysical properties of polymers and morphology of blend films, and also have a significant influence on devices performance.
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Russell, T. P., V. R. Deline, V. S. Wakharkar, and G. Coulon. "Behavior of Block Copolymers in Thin Films." MRS Bulletin 14, no. 10 (October 1989): 33–37. http://dx.doi.org/10.1557/s0883769400061479.
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The uses of polymeric materials in today's world are vast. Polymers are finding applications in the microelectronics industry as dielectric insulators and photoresists, in the aerospace and automobile industry as lightweight substitutes for metals, and in biotechnology as replacement components for bone, heart, and other organs. These are just a few of the many end uses of polymers.Often, a polymer may have a particular, desirable property but processing of the polymer is difficult or the polymer's surface characteristics are undesirable. To circumvent such shortcomings there are several options. The first is to synthesize a new material, which is quite costly and time consuming. Alternatively, two polymers with complimentary properties can be mixed. Unfortunately, most polymer pairs are immiscible unless there are specific interactions (e.g., hydrogen bonding) between the two components. Consequently, coarse phase separation is often observed, leading to an ill-defined material. Finally, two chemically distinct homopolymers can be joined together at one point, forming a block copolymer. While phase separation may occur, the scale of the domains is restricted to the sizes of the individual homopolymers, which is typically on the tens of nanometers scale. The added advantage of this approach is that the size of the different blocks can be altered, varying the concentration of the different components. For copolymers that “microphase” separate, this variation in composition leads to a variation of the morphology of the microdomains ranging from spherical to cylindrical to lamellar.
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Spontak, R. J. "Direct casting of SBS block copolymers on supported grids for TEM study." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 788–89. http://dx.doi.org/10.1017/s0424820100145285.
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Transmission electron microscopy (TEM) has been used successfully in studying the microstructures resulting from microphase-separated block copolymers consisting of polystyrene (S) and polybutadiene (B). Difficulty, however, arises in the sample preparation stage, in which specimens ranging 50-100 nm thick are required. Such specimens can be obtained by either cutting ultrathin sections from a bulk sample or by dissolving the polymer in a suitable solvent and casting the solution to form an ultrathin film. Many methods exist for preparing such films, and almost all share one common feature: the cast film is floated on a clean fluid (e.g., water) surface. In some cases, the film is first cast on a carboncoated glass slide and scored prior to the flotation step so that small sections may be picked up by TEM grids. To avoid (a) casting the copolymer onto a flotation medium, which may inadvertently affect the microstructure orientation, (b) excessive handling of the cast film, and (c) exposing a hygroscopic copolymer (e.g., siloxane polyimide polymers) to a water surface, a method of casting copolymer films directly onto supported TEM grids is presented here.
Dissertations / Theses on the topic "Microphases. eng"
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Godoy, Wagner Lopes de. "Efeito da temperatura de pré-aquecimento e características do pulso na microestrutura de aço estrutural de alta resistência e baixa liga soldado com arco elétrico e proteção gasosa /." Bauru : [s.n.], 2008. http://hdl.handle.net/11449/90822.
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Orientador: Yukio KobayashiBanca: Carlos Alberto Soufen
Banca: Antônio de Padua Lima Filho
Resumo: A identificação e a qualificação dos constituintes microestruturais de uma junta soldada são de grande importância pela relação que existe entre a microestrutura do cordão e as propriedades mecânicas, particularmente a tenacidade. Trabalhando com variações nos parâmetros de pulso, corrente de pico e tempo de pico, e também na temperatura de pré-aquecimento, foram quantificados os constituintes ferrita acicular e microfases presentes no metal de solda; sendo ambos considerados controladores da tenacidade. Os resultados deste trabalho demonstraram que aumentou a quantidade de ferrita acicular para os menores níveis dos parâmetros de pulso e da temperatura de pré-aquecimento. Quanto às microfases, ocorreu uma redução na quantidade à medida que se elevaram os níveis dos parâmetros de pulso e da temperatura de pré-aquecimento. Observou-se, também, qual foi a influência da velocidade de resfriamento na microestrutura final do metal de solda. Foi utilizado o processo de soldagem a arco elétrico com proteção gasosa, no modo pulsado e arame tubular. A soldagem foi realizada em chapa de aço estrutural de alta resistência e baixa liga (COS-AR 50), com chanfro em "X" e ângulo de 30º. Como metal de adição foi utilizado o arame tubular de fluxo metálico E70C-6M, com diâmetro de 1,2 mm.
Abstract: The identification and qualification of the microstructural constituents present in the welded joint are very important for the relationship between the microstructure of the weld beads with the mechanical properties, particularly toughness. Working with variations of pulse parameters, peak current and peak time, and also preheating temperature, had been quantified the constituents acicular ferrite and microphases present in weld metal; being both considered controllers of toughness. The results of this work demostrated that greater amounts of acicular ferrite had been occurred in the lowest levels of pulse parameters and preheating temperature. As for microphases, it has a reduction of the amount with the increase of pulse parameters and preheating temperature. It was observed, also, the influence of the cooling speed in the final microstructure of the weld metal. The samples were welded by the metal gas arc welding, using pulsed arc and tubular wire. As metal base was used HSLA structural steel plate (COS-AR 50), with "X"-groove and bevel angle 30º. The addition metal was the tubular metal-cored wire "E70C-6M" with diameter of 1.2 mm.
Mestre
Book chapters on the topic "Microphases. eng"
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Erman, Burak, and James E. Mark. "Networks with Semiflexible Chains and Networks Exhibiting Strain-Induced Crystallization." In Structures and Properties of Rubberlike Networks. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195082371.003.0014.
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Classical theories of rubber elasticity are based on models of flexible polymer chains that are sufficiently long to exhibit Gaussian behavior as described in chapter 1 and in appendix F. Additionally, the chains are phantomlike in the sense that they do not interact with one other along their contours. The theories described in chapter 2 were based on this picture of the individual chain. In this chapter, we describe the elasticity of networks that depart substantially from those addressed in the classical theories. The departures may result from two sources: (1) the chains may be only semiftexible, as a result of which the segments of neighboring chains compete for space in the deformed network, and choose preferentially oriented configurations, and (2) the chains may form crystallites, upon deformation, as a result of which the homogeneous structure of the classical network model may be transformed into a nonhomogeneous one having microphases of crystalline and amorphous regions. The subject of crystallization under deformation, for networks in general, is relatively old, and has been treated in some detail in previous studies. For this reason, crystallization and some of its effects will be reviewed only briefly at the end of this chapter. The main emphasis will be given to networks with semiflexible chains. Examples of networks with semiflexible chains are those in which the chains have rodlike segments separated by flexible spacers, or those where the chains have bond angles appreciably larger than tetrahedral. Incorporation of these chains into a network structure results in materials that exhibit segmental orientations significantly larger than those shown by classical networks. Specific examples would include networks prepared from aromatic polyamide chains or from chains containing liquid-crystalline sequences along the direction of the backbone. Because of their unique chain structures, these networks are easily orientable, at the molecular level, by macroscopic deformations. The orientational transitions may easily be controlled by application and removal of anisotropic strains, and are therefore of great technological interest for use in optical devices. Other examples of networks with easily orientable chains are those with rigid sequences in the side groups.
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Han, Chang Dae. "Continuum Theories for the Viscoelasticity of Flexible Homogeneous Polymeric Liquids." In Rheology and Processing of Polymeric Materials: Volume 1: Polymer Rheology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195187823.003.0008.
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There are two primary reasons for seeking a precise mathematical description of the constitutive equations for viscoelastic fluids, which relate the state of stress to the state of deformation or deformation history. The first reason is that the constitutive equations are needed to predict the rheological behavior of viscoelastic fluids for a given flow field. The second reason is that constitutive equations are needed to solve the equations of motion (momentum balance equations), energy balance equations, and/or mass balance equations in order to describe the velocity, stress, temperature, and/or concentration profiles in a given flow field that is often encountered in polymer processing operations. There are two approaches to developing constitutive equations for viscoelastic fluids: one is a continuum (phenomenological) approach and the other is a molecular approach. Depending upon the chemical structure of a polymer (e.g., flexible homopolymer, rigid rodlike polymer, microphase-separated block copolymer, segmented multicomponent polymers, highly filled polymer, miscible polymer blend, immiscible polymer blend), one may take a different approach to the formulation of the constitutive equation. In this chapter we present some representative constitutive equations for flexible, homogeneous viscoelastic liquids that have been formulated on the basis of the phenomenological approach. In the next chapter we present the molecular approach to the formulation of constitutive equations for flexible, homogeneous viscoelastic fluids. In the formulation of the constitutive equations using a phenomenological approach, emphasis is placed on the relationship between the components of stress and the components of the rate of deformation (or strain) or deformation (or strain) history, such that the responses of a fluid to a specified flow field or stress can adequately be described. The parameters appearing in a constitutive equation are supposed to represent the characteristics of the fluid under consideration. More often than not, the parameters appearing in a phenomenological constitutive equation are determined by curve fitting to experimental results. Thus phenomenological constitutive equations shed little light on the effect of the molecular parameters of the fluid under investigation to the rheological responses of the fluid.
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Han, Chang Dae. "Experimental Methods for Measurement of the Rheological Properties of Polymeric Fluids." In Rheology and Processing of Polymeric Materials: Volume 1: Polymer Rheology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195187823.003.0010.
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There has been a continuing interest in developing experimental techniques for the measurement of the rheological properties of viscoelastic fluids. As discussed in Chapter 3, reliable experimental data are needed in order to evaluate the effectiveness of a constitutive equation in its ability to predict the rheological properties of viscoelastic fluids. Also, as is presented in later chapters, a better understanding of the rheological properties of polymers is very important for the determination of optimum processing conditions, as well as for the attainment of desired physical/mechanical properties in the finished product. Further, reliable measurement of the rheological properties of polymers can be used to control polymerization reactors in industry and also to control polymer processing operations. In this chapter, we present experimental methods for measurement of the rheological properties of polymeric fluids. For this, we discuss experimental methods to determine (1) steady-state simple shear flow and oscillatory shear flow properties using cone-and-plate rheometry, (2) steady-state shear flow properties using capillary/slit rheometry, and (3) elongational flow properties of polymeric fluids. There are other rotational types of rheological instruments, such as those with concentric-cylinder and eccentric-parallel plates. However, such rheological instruments are not widely used today and thus in this chapter we do not present the principles and applications of such rheological instruments. In presenting the experimental methods for rheological measurements we refer to the fundamentals presented in Chapters 2 and 3. For further details of the experimental methods, there are monographs (Collyer and Clegg 1998; Dealy 1982; Ferry 1980; Walter 1975) that are devoted entirely to the discussion of rheological measurements. The primary purpose of this chapter is to demonstrate how the fundamentals presented in Chapters 2–4 can be used in the measurement of the rheological properties of polymeric fluids. Optical rheometry is an important experimental technique for investigation of the relationship between any microphase morphology dynamics and the rheological behavior of complex polymeric fluids (e.g., liquid-crystalline polymers), which exhibit strong chain orientation during flow (Fuller 1995).
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Han, Chang Dae. "Rheology of Block Copolymers." In Rheology and Processing of Polymeric Materials: Volume 1: Polymer Rheology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195187823.003.0014.
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Block copolymer consists of two or more long blocks with dissimilar chemical structures which are chemically connected. There are different architectures of block copolymers, namely, AB-type diblock, ABA-type triblock, ABC-type triblock, and AmBn radial or star-shaped block copolymers, as shown schematically in Figure 8.1. The majority of block copolymers has long been synthesized by sequential anionic polymerization, which gives rise to narrow molecular weight distribution, although other synthesis methods (e.g., cationic polymerization, atom transfer radical polymerization) have also been developed in the more recent past. Owing to immiscibility between the constituent blocks, block copolymers above a certain threshold molecular weight form microdomains (10–50 nm in size), the structure of which depends primarily on block composition (or block length ratio). The presence of microdomains confers unique mechanical properties to block copolymers. There are many papers that have dealt with the synthesis and physical/mechanical properties of block copolymers, too many to cite them all here. There are monographs describing the synthesis and physical properties of block copolymers (Aggarwal 1970; Burke and Weiss 1973; Hamley 1998; Holden et al. 1996; Hsieh and Quirk 1996; Noshay and McGrath 1977). Figure 8.2 shows schematically four types of equilibrium microdomain structures observed in block copolymers. Referring to Figure 8.2, it is well established (Helfand and Wasserman 1982; Leibler 1980) that in microphase-separated block copolymers, spherical microdomains are observed when the volume fraction f of one of the blocks is less than approximately 0.15, hexagonally packed cylindrical microdomains are observed when the value of f is between approximately 0.15 and 0.44, and lamellar microdomains are observed when the value of f is between approximately 0.44 and 0.50. Some investigators have observed ordered bicontinuous double-diamonds (OBDD) (Thomas et al. 1986; Hasegawa et al. 1987) or bicontinuous gyroids (Hajduk et al. 1994) at a very narrow range of f (say, between approximately 0.35 and 0.40) for certain block copolymers. Figure 8.2 shows only one half of the symmetricity about f = 0.5. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) have long been used to investigate the types of microdomain structures in block copolymers.