Crystallization,Melting and Morphology of Syndiotactic/Atactic Polystyrene Blends: Molecular Weight Effects of Atactic Polystyrene

Summary: Molecular weight (MW) effects of atactic polystyrene (aPS) on the morphologies and crystallization kinetics of syndiotactic polystyrene (sPS) blends have been investigated, and miscibility was confirmed for all the sPS/aPS blends. Addition of aPS(M) or aPS(L) leads to a significant increase in the entropy of mixing and gives rise to a pronounced decrease in the equilibrium melting temperature of the blends. On heating from the glassy state, the crystallization peak temperature of the sPS/aPS(H) blend increased with increasing aPS content due to a dilution effect, whereas those of sPS/aPS(M) and sPS/aPS(L) decreased mainly due to enhanced chain mobility. On cooling from the melt state, the crystallization peak temperature decreased with increasing aPS content regardless of the aPS MW. A higher activation energy is required for the sPS component transport from the miscible melt to the growth front in the sPS/aPS(L), suggesting that extra energy is required for the demixing process. Interspherulitic segregation of aPS diluents was evident in the sPS/aPS(L) blends, while interfibrillar segregation morphology was obtained in the sPS/aPS(H) as well as the sPS/aPS(U) blends.

SEM images of sPS/aPS blends 50/50(L) at 230 °C (C) and 70/30(L) at 250 °C (D).     

Thermal‐Induced Crystal/Conformation Transformations in Syndiotactic Polystyrene Films Treated with Different Solvents

Solution‐crystallized or solvent‐induced crystal forms and transitions of these crystals upon post‐annealing in solvent‐treated syndiotactic polystyrene (sPS) (films cast from o‐dichlorobenzene or immersed in 1,2‐dichloroethane, respectively) were investigated via wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and Fourier‐transform infrared (FTIR) spectroscopy. IR spectra in the frequency range of 720–820 cm^?1, which is attributed to the C? H out‐of‐plane bending of the phenyl ring for neat syndiotactic polystyrene (sPS) and their crystal/solvent complexes (sPS/o‐dichlorobenzene or sPS/1,2‐dichloroethane), were examined for the freshly as‐cast samples in comparison with those having been subjected to post‐annealing by heating to high temperatures. Three bands centered at approximately 779, 769, and 750 cm^?1 were observed, the intensity and wavenumber being sensitive to the helical structural changes as a function of the annealing temperature. The band at 769 cm^?1, being associated with the intramolecular interactions of the helical chains of the γ‐crystal, was used to confirm the formation of such a phase. The bands at 779 cm^?1 and 769 cm^?1 disappeared and the sharper band at 750 cm^?1 remained upon further annealing above the γ → α′ transition temperature. Thus, by examining the temperature dependency as revealed in the IR spectra, the thermal‐induced phase transition from the δ‐ to an ordered γ‐ and then to an α′‐phase was successfully proven for the sPS/o‐dichlorobenzene complex. Similarly, the other sPS/1,2‐dichloroethane complex underwent transition (from a δ‐ to a disordered γ‐ and then to an α′‐phase) upon the same thermal treatments, except that the intermediate phase is a disordered γ‐phase.

FTIR spectra in the frequency ranging from 720 to 820 cm^?1 for the δ‐type sPS/o‐dichlorobenzene complex subjected to increase of the temperature by 5 °C steps in the range of 60–245 °C.     

Crystallization and Morphological Features of Syndiotactic/Atactic Polystyrene Blends at High Temperatures

Crystalline/amorphous binary mixtures of polystyrene with different tacticities, syndiotactic/atactic isomers (sPS/aPS), have been systematically studied to reveal the composition dependence of the blend morphologies, i.e., sPS lamellar structure and aPS diluent segregation, developed after isothermal crystallization. To reveal the molecular weight effect of the aPS diluents, four different of aPS were used to prepare blends with various compositions. After being melt crystallized isothermally at 250 °C, all blends were investigated by means of POM, WAXS, and SAXS as well as SEM and TEM to reveal the spherulitic and lamellar morphologies developed.

     

Syndiotactic Polystyrene Containing ortho‐Dichlorobenzene: Crystal Structure of the Clathrate Form

Summary: The crystal structure of the clathrate form of syndiotactic polystyrene containing ortho‐dichlorobenzene has been determined, and compared with those of the other crystalline clathrate structures of s‐PS already known. This guest molecule, characterized by a quite different shape and volume from the others already described, gives rise to the only example of clathrate form of s‐PS presenting a statistical orthorhombic symmetry (cell constants a = 17.5 Å, b = 22.9 Å, c = 7.8 Å and space group Ccmb). This symmetry is generated by the random coexistence in the crystals of domains, with the same monoclinic P2₁/a symmetry found for the other clathrate forms, that can be realized by two different but energetically equivalent packings of the chains. The unit cell constants are a = 17.5 Å, b = 14.4 Å, c = 7.8 Å and γ = 127.4°. The shape of the guest molecule produces a significant modification of the cavities (if compared to δ form) realized mainly through a shift of the ac layers of chains delimiting the cavities along the a axis direction that turns out in the highest γ value found for these kinds of structures.

Schematic representation of the arrangement of the chains according to the orthorhombic (solid line) and to the monoclinic (dotted line) unit cells proposed for the crystal structure of the clathrate form of s‐PS containing o‐DCB.     

Syndiotactic Polystyrene Films with Different Uniplanar Orientations: Additional Information on Crystal Phase Transitions

Syndiotactic polystyrene δ form films, exhibiting a_//c_// and a_?c_// uniplanar orientations and subjected to annealing procedures in the temperature range of 60–130 °C, have been thoroughly characterized by X‐ray diffraction. The reported results indicate that the gradual irreversible transformation from the nanoporous δ phase toward the dense γ phase occurs with a continuous transformation of the 010 and reflections of the δ form into the 020 and 200 reflections of the γ form, respectively. This analysis allows ruling out of the occurrence of a new reflection typical of an intermediate phase, as suggested by X‐ray diffraction measurements on unoriented or axially oriented samples.     

On the Crystal Structure of the Clathrate Forms of Syndiotactic Polystyrene Containing Carbon Disulfide and Iodine

Summary: The crystal structure of the clathrate form of syndiotactic polystyrene containing different amounts of CS₂ has been analyzed, and compared with that of the clathrate containing I₂. These two guest molecules, which are characterized by a similar shape and volume, give rise to the only two known examples of clathrate forms containing up to two molecules per cavity. The two structures are isomorphous both in the case of complete and of partial occupation of the cavities. In the second case, CS₂ and I₂ molecules when alone in the cavity occupy almost identical positions at its center. Some of the literature on the crystal structure of these two clathrates is ambiguous and this is discussed. A comparison with the CS₂ clathrates of syndiotactic poly(p‐methylstyrene) and poly(m‐methylstyrene) is also made.

Schematic representation of the two ways in which guest molecules can be hosted in the cavities of the crystals of the s‐PS clathrate form containing carbon disulfide.     

Surface Modification of Polystyrene Films. Depth Profiling and Mapping by Raman Microscopy

The chemical modification of polymer films was studied using Raman microscopy. The nitration of polystyrene films (PS) in a non‐swelling reaction medium was compared with the nucleophilic substitution of chlorine atoms by cyano groups in poly(p‐chloromethylstyrene) (PSC) films in mixtures of a good and a non‐solvent for the polymer. Using Raman microscopy in the confocal mode, depth profiles of films modified in different conditions were recorded. In both reactions, conditions could be found which allowed the polymer films to be preferentially modified at the surface. The gradient of the degree of modification and the surface selectivity are functions of reaction time, temperature and solvent quality. The homogeneity of the modification reactions was compared by mapping of surface areas using Raman spectroscopy in the conventional mode.     

Quantitative Correlation between Steric Defects and Thermal Behavior in Highly Syndiotactic Polystyrene: A Study Based on DSC and 13C NMR Spectroscopy

Several syndiotactic polystyrene (sPS) samples have been synthesized by using different catalytic systems. Their stereochemistry has been determined by ¹³C NMR spectra in both the aliphatic CH₂ and aromatic C₁ resonance regions. The observed peaks have been unambiguously assigned to specific hexads and heptads, respectively, and their intensities have been used to draw the percent of defects (meso dyads) in the polymer chains. On the hypothesis that chain defects are at the origin of chain folding and thus determine the thickness of crystalline lamellae, we performed differential scanning calorimetry (DSC) analysis on the same samples, and their thermal parameters were measured. A model was developed to determine the amount of steric defects from the DSC melting‐peak profiles, and the results obtained were compared with the NMR results. A satisfactory agreement was found (correlation factor 0.96) in the explored range of defect concentrations (up to 2.5% of meso dyads). The possible influence of the extraction procedure of the amorphous fraction was found to be negligible. Thus, information on stereochemistry can be obtained from DSC experiments starting from as‐prepared (not extracted) samples.

     

Nanoindentation of Films of Perfluorotridecyl,Perfluorodecyl, and Perfluoroheptyl End‐Functionalized Polystyrene at the Micron Scale

Polystyrenes (PS) end‐functionalized with perfluorotridecyl (PFTD), perfluorodecyl (PFD), and perfluoroheptyl (PFH) groups are synthesized using the corresponding perfluoroalkyl initiators by atom transfer radical polymerization. Polymer thin films deposited on silicon wafers are studied by dynamic nanoindentation (NI). NI measurements of the 15k PFTD‐PS sample showed increases of about 80 and 300% in the storage and loss moduli, respectively, compared to the 15k PS homopolymer. Measurements made on different regions of the PFTD‐functionalized PS show a fivefold greater standard deviation compared to the 15k PS homopolymer. The effects for the PFD and PFH groups are smaller in all respects consistent with expectations.

     

1,4‐Bisbenzil: Visible‐Light‐ and Heat‐Assisted Crosslinking of Polystyrene Films

Polystyrene (PS) film containing 1,4‐bisbenzil is efficiently crosslinked in two steps. In the first step, visible light (λ > 400 nm) causes molecular oxygen to insert between two carbonyl groups of one of the 1,2‐dicarbonyl groups. The peroxide is subsequently decomposed by absorption of another photon, forming acyloxy radicals, which add to the aromatic ring of the PS chain. The remaining 1,2‐dicarbonyl group is then photoperoxidized to form PS with pendant benzoyl peroxide moieties. In the second step, pendant benzoyl peroxide groups are decomposed thermally to form acyloxy macroradicals responsible for the crosslinking. Crosslinking proceeds simultaneously with degradation. Finally, the gel content in the film may exceed 80 wt%.

     

The Orientation and Photophysical Properties of Conjugated Polymers in Oriented Films

Highly oriented light‐emitting blend films containing poly(9,9‐dioctylfluorene) (PFO), PFO with one fluorenone unit (PFF), and ultrahigh‐molecular‐weight polyethylene (U‐PE) are prepared by using a tensile deformation technique. A high dichroic ratio of 36 in photoluminescence from the oriented film is obtained. The photophysical properties of the PFF/PFO blend are investigated in the blend films. In particular, the origin of the green band (‘g‐band’) that often undesirably appears from PFO used in air, is discussed in such a highly oriented circumstance. The experimental results powerfully demonstrate that the g‐band originates from the mono‐chain fluorenone moieties, rather than the fluorenone‐based excimer.

     

Polystyrene sulphonates and aspiration pneumonia: a histochemical study

The histochemical characteristics of a sulphonated polystyrene resin were investigated and compared with those of sulphonic acid residues derived from intrinsic tissue components. The major features of the resin particles were their direct Schiff positivity and basophilia. Unlike the tissue sulphonic acids, the resin particles failed to stain with alcian blue. Because of their acid nature, the particles may be responsible for the onset of an aspiration pneumonia if they are accidentally inhaled by debilitated patients.     

游戏治疗的历史演变与发展取向

游戏治疗起源于精神分析，弗洛依德开创了儿童心理治疗与游戏结合之先河。综观游戏治疗近百年发展的历史，可以发现其大致经历了三个主要发展阶段：精神分析游戏治疗、结构主义游戏治疗、人本主义游戏治疗：逐步形成了两个基本模式：集中性游戏治疗与非指导性游戏治疗。目前，游戏治疗自身正孕育着一场革新：日益强调治疗师的角色特征以及对文化的适应性；游戏的诊断价值与治疗功能的双重变革；短期游戏治疗的兴起；游戏治疗对象的专门化程度日益提高。     

Molecular and Microdomain Orientation in Semicrystalline Block Copolymer Thin Films by Directional Crystallization of the Solvent and Epitaxy

The directional crystallization of crystallizable organic solvents and the subsequent epitaxial crystallization of crystalline blocks onto the surface of crystalline substrates in semicrystalline block copolymers, control both molecular chain orientation of the crystalline block and the microdomain structure of the block copolymer. Thin film of semicrystalline polystyrene‐block‐poly(ethylene‐alt‐propylene)‐block‐polyethylene (PS/PEP/PE) terpolymer and polystyrene‐block‐polyethylene (PS/PE) diblock copolymer, which both contain crystallizable polyethylene (PE) blocks, have been patterned using benzoic acid (BA) and anthracene (AN) as crystallizable solvents. The directional crystallization induces orientation of the microdomains and epitaxy, due to the crystallographic matching of unit cells between the crystalline PE blocks and the crystalline organic substrates, resulting in the development of highly aligned crystalline PE blocks. The orientation of the PE crystals onto the substrate is evidenced by selected area electron diffraction and bright field transmission electron microscope images. In the case of the PS/PEP/PE terpolymer, the process induces the PS cylinders to align parallel to the b axis of the BA crystals. Long crystalline PE lamellae are oriented edge‐on on the BA surface, with the b axis of PE parallel to the b axis of BA, and parallel to the PS cylinders. In the case of the PS/PE diblock copolymer, the PE cylinders are oriented perpendicular to substrate, packed on a hexagonal lattice. Each cylinder contains precisely one crystalline PE lamella oriented edge‐on on the substrate. When BA is used, the PE lamellae inside cylinders are oriented with the b axis parallel to the b axis of BA crystals. When AN is used, due to the different epitaxial relationship between PE block and AN crystals, the PE lamellae are oriented along two equivalent directions, with the c axis parallel to the [110] and direction of AN crystals.

Schematic model of the final microstructure generated by combination of the directional crystallization and epitaxy.     

Flow‐Induced Orientation in Miscible Crystalline Polymer Blends of Poly(vinylidene fluoride) and Poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)]

Oriented films of miscible polymer blends of poly(vinylidene fluoride) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] were prepared using a flow‐orientation technique. The lamellar structure and crystal orientation depended upon composition and flow temperature (T_flow). An interlamellar exclusion structure was induced in the blend flow‐oriented below 150 °C, whereas an interlamellar inclusion structure was developed above 150 °C. The crystal orientation of PHBHV was affected by the lamellar structures because the PHBHV chains crystallized in the pre‐existing crystalline morphology of PVDF. Crystallization of PHBHV was markedly restricted at lower PHBHV contents.

     

Polymer‐Dispersed Liquid Crystals Based on Polystyrene and EBBA: Analysis of Phase Diagrams and Morphologies Generated

As an example of thermoplastic/liquid crystal blends that do not exhibit a liquid‐liquid immiscibility region in their phase diagrams, a polystyrene (PS)/N‐4‐ethoxybenzylidene‐4′‐butylaniline (EBBA) blend was analyzed. The complete phase diagram was built up using thermal transitions determined by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The boundary of the nematic + isotropic region was fitted with the Flory‐Huggins‐Maier‐Saupe model, extended to consider the polydispersity of PS. Main factors controlling the morphologies generated by thermal‐induced phase separation (TIPS) were the initial EBBA concentration in the blend and the cooling rate. Cooling at a fast rate led to small nematic domains with a narrow size distribution. Slow cooling rates led to the coexistence of very large and small dispersed domains. This was because of the large extent of coalescence of the droplets first generated associated with the continuation of the nucleation/growth process in a medium of increasing viscosity. The use of fast cooling rates might be important for the generation of a narrow size‐distribution of nematic droplets by TIPS in polymer‐dispersed liquid crystals (PDLC) used in electrooptical devices.

Micrograph obtained by transmission optical microscopy without crossed polarizers, showing nematic domains dispersed in a glassy matrix arising by a fast cooling of the blend from 130 °C; composition of blend: 70 wt.‐% EBBA.     

Coordinative Layer‐by‐Layer Assembly of Thin Films Based on Metal Ion Complexes of Ligand‐Substituted Polystyrene Copolymers and Their Use as Separation Membranes

Polystyrene copolymers containing either 4′‐vinyl‐2,2′:6′,2″‐terpyridine (P1) or 2,6‐bis(1‐methyl‐1H‐benzo[d ]imidazol‐2‐yl)pyridin‐4‐yloxy)‐methacrylate (P2) as comonomers are prepared and studied on metal ion coordination in solution and coordinative sequential assembly of films and membranes. Permeation and separation of ions and neutral aromatic molecules across the membranes are investigated. UV–vis titration of P1 with zinc acetate in chloroform/methanol (25:1) indicates formation of 2:1 ligand:metal bis‐complexes, while titration of P2 led to 1:1 monocomplexes. It is demonstrated that coordinative interactions between the ligand groups and metal ions such as Zn(II) or Cu(II) can be used for layer‐by‐layer assembly of ultrathin films on solid quartz supports and porous supporting membranes. Formation of coordination polymer assemblies is characterized using UV‐spectroscopy, quartz crystal microbalance measurements, scanning electron microscopy, and thickness measurements. Coordinative films prepared on porous polyacrylonitrile/polyethylene terephthalate supporting membranes exhibit a selective transport of ions and small molecules. Ion transport in aqueous and alcoholic solution is controlled by a sieving effect and by electrostatic rejection at the ligand–metal ion complexes in the membrane. The transport of organic aromatic molecules is only controlled by the sieving effect. Separation factors α(NaCl/BaCl₂) up to 4.2 and α(naphthalene/perylene) up to 4.8 are found.

     

Long Chain Polyamides: Influence of Methylene Sequence Length and External Forces on Structural Features

Crystallographic studies on a series of even–even polyamides PA10.n (12, 14, 16, and 18) with variable methylene sequence length (n − 2) are performed. Temperature-dependent X-ray diffraction studies show that a triclinic α phase is the preferred polymorph after slow cooling to room temperature like in many other even–even polyamides. For PA10.12 and PA10.14 the pseudo-hexagonal high temperature phase γ is observed between the Brill transition temperature T_B and melting point T_M. For both higher members a distinct Brill transition is absent below T_M. The influence of temperature on the packing state of the stems during cooling is discussed and compared to related polymers. An analysis of well oriented crystalline states in annealed fibers reveals that the crystalline state achieved under ambient conditions is influenced by external forces due to small energetic differences between different α and β polymorphs. All PA10.n samples show in the fiber-oriented state a prominent β polymorph which is dominant in PA10.12 and PA10.14 but superimposed with a significant α fraction in both higher members. The consequences of changes in the polymorphic state under the influence of external forces for crystalline states achieved under application relevant processing conditions are considered.     

Photocontrol of Birefringence and In‐Plane Molecular Orientation in Copolymer Liquid Crystal Films with 4‐Methoxyazobenzene and Photo‐Cross‐Linkable Side Groups

Control of the in‐plane orientation direction in a polymethacrylate copolymer liquid crystal film substituted with 4‐methoxyazobenzene (4MAz) and 4‐methoxycinnamoyloxybiphenyl (4MCB) side groups, and control of the reversible birefringence of the resultant oriented film are described. High‐order in‐plane molecular orientation was generated by irradiating with linearly polarized (LP) 365 nm light and subsequent annealing. By adjusting the exposure dose, the reorientation direction was controlled parallel and perpendicular to the electric vector ( E ) of the LP light. Cooperative reversion of the orientation direction for both the 4MAz and 4MCB groups was observed, and the orientational order, S, varied from ?0.79 to +0.75, without the side groups aggregating. The degree of the photoreaction and the distribution of the photoproducts from the 4MAz and 4MCB side groups through the axis‐selective photoreaction explain the reversion of the orientation direction. Optical recording, erasing, and birefringent control of the resultant oriented films were demonstrated by employing the photoisomerization of the 4MAz side groups using nonpolarised (NP) 405 nm light.

Order parameters of a P1 film after irradiating with LP 365 nm light (circles) and that following subsequent annealing (squares), as a function of exposure energy.