The synthesis and the microstructural characterization of isotactic poly (N‐pentenyl‐carbazole) (i‐PPK) are reported. The achieved polymer is semicrystalline, the melting temperature is 138°C. i‐PPK Fourier transform infrared spectroscopy (FTIR) spectrum and X‐ray diffraction pattern are compared with those of polyvinylcarbazole. The observed differences are tentatively associated to higher flexibility of the i‐PPK chains due to the alkylene group connecting the carbazole group to the main chain. The presence of intrachain and interchain interactions between carbazole units, which bring these groups to stack each other, is assumed. i‐PPK optical properties are investigated and an electroluminescent behaviour of polymer is observed. Organic light emitting diodes based on i‐PPK layers are founded to emit white light. POLYM. COMPOS., 36:1110–1117, 2015. © 2015 Society of Plastics Engineers

Optical recording technology has a major advantage over other recording technologies, namely, that reading and writing of data is accomplished by light, so that no physical contact between the media and the optical head occurs. The storage capacity of these optical media (e.g., disks) is limited by the size of the smallest marks on their surfaces that can be read by the wavelength of light used. In this communication, we present a possible data storage system with molecular-sized (» 200 3 ) marks that also give, in principle, the possibility to record information depthwise, rather than just on the material surface.Photoreactions of organic dyes, generally added or covalently bonded to stable and transparent polymeric materials, have been widely used as means of recording optical data. In particular, photoisomerizations are often preferred to other reactions (like, e.g., photopolymerizations) due to the negligible dimensional changes associated with recording. These photoisomerization reactions have to cause some change in the optical properties of the exposed regions of the opticalrecording material, such as changes in the absorption or fluorescence spectrum, or the refractive index.It is well known that norbornadiene and its derivatives (N, see Scheme 1; h: Planck's constant; m: radiation frequency; k: radiation wavelength) are easily photoisomerized into quadricyclane and its derivatives (Q, see Scheme 1) upon UV irradiation. Photoisomerization of N has been widely investigated in organic solutions [1] as well as in aqueous media [2] and, more recently, in organic polymers. [3,4] In particular, polymeric materials containing N derivatives, both as covalently bonded pendant groups [3] or simply added to transparent amorphous phases, [4] have been investigated for use as optical waveguides (utilizing photoinduced refractive-index changes) and for data storage.In recent years, we have extensively studied a nanoporous crystalline phase (the so-called d phase) of syndiotactic polystyrene (s-PS), which has two identical cavities and eight styrene monomeric units per unit cell, [5] and which is promising for applications in chemical separation, air/water purification, and sensorics. [6] In fact, it rapidly and selectively absorbs (both from the gas phase [6a,e±g] and aqueous solutions [6b,d] ) suitable guest molecules even at very low activities, generally absorbing only one isolated guest molecule per cavity. [5,7] Moreover, studies of guest-desorption kinetics [6c] and of gas transport [6g] on s-PS films have shown that the guest diffusivity in the d phase is much lower than in the amorphous phase. The latter feature is quite relevant since it assures a higher stability of the doping of this crystalline phase with respect to the usual doping of amorphous phases. We have included N as the isolated guest of the host d crystalline phase of robust s-PS polymer films, and we have achieved efficient valence photoisomerization of N to Q in this polymeric crystalline phase. In fact, it will be shown that no...

The sorption and desorption of a guest (1,2-dichloroethane) in syndiotactic polystyrene (s-PS) films, presenting three different kinds of uniplanar orientation ((010), (2 h10), or (002)) of the nanoporous host δ phase, have been investigated, mainly by Fourier transform infrared measurements. For guest uptake from dilute aqueous solutions (e.g., 50 ppm), the sorption in the amorphous phase is negligible with respect to sorption in the nanoporous crystalline phase. Correspondingly the guest sorption and desorption kinetics are influenced by the orientation of the anisotropic host crystalline phase. In particular, as for the guest diffusivity (D) measured by both sorption and desorption experiments, D(010) e D(002) < D(unoriented) < D(2 h10). These results can be rationalized on the basis of previous molecular dynamics simulations, predicting an anisotropic guest diffusion in the δ crystalline phase.

The self-assembling of fluorescent guest molecules, with the δ nanoporous host crystalline phase of syndiotactic polystyrene (s-PS) films, reduces chromophore diffusivity. Moreover, the chromophore fluorescence can be largely perturbed by formation of suitable polymer co-crystals. In particular, by excitation at the absorbance maximum (≈265 nm), s-PS/1,3,5-trimethylbenzene clathrate co-crystals present a broad fluorescence band nearly centered at 300 nm, while the corresponding intercalate co-crystals present a red-shifted fluorescence band with maxima at 330, 340, and 355 nm. This red shifted fluorescence is possibly due to absorption of the primary fluorescence by ground state complexes, formed in the intercalate co-crystal. The enhanced and red-shifted fluorescence could be relevant for optical and optoelectronic applications.

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The electroluminescence (EL) of isotactic and syndiotactic poly(N-pentenyl-carbazole) (PPK), achieved by coordination polymerization, is studied in order to investigate the interrelation between thepolymer tacticity and theirphysical-chemical properties. The use of these polymers in organic light-emitting diode (OLED) fabrication is also explored. Thermal and x-ray diffraction analyses of PPKs show that the isotactic stereoisomer is semicrystalline, whereas the syndiotactic one is amorphous. Optical analysis of both stereoisomers, carried out on film samples, reveals the presence of two different excimers:'sandwich-like' and 'partially overlapping'. Nevertheless, the emission intensity ratio between 'sandwich-like' and 'partially overlapping' excimers is higher in the isotactic than in the syndiotactic stereoisomer. Using the synthesized polymers as OLED emitting layers, the influence of the polymer tacticity on theEL properties of the device is highlighted. In detail, while blue OLEDs are obtained by using the syndiotactic stereoisomer, OLEDs witha multilayer structure fabricated with the isotactic stereoisomer emit white light. The contribution of three different emissions (fluorescence, phosphorescence and electromer emissions) with comparable intensities to the detected white light is discussed.

Syndiotactic polystyrene (s-PS) films including a fluorescent guest (naphthalene, NP) in their nanoporous δ crystalline phase have been prepared and characterized by X-ray diffraction, infrared linear dichroism, molecular modeling, and fluorescence depolarization techniques. A nearly perpendicular orientation of the fused rings of NP guest molecules with respect to the chain axis of the δ crystalline structure has been established by molecular mechanics and by evaluation of directions of transition moment vectors of infrared vibrational modes. The fluorescence depolarization is more efficient for NP guest molecules into the host phase than for NP molecules simply absorbed in the amorphous phase. This could be due to a more efficient resonance energy transfer between guest molecules, possibly associated with their ordered positioning and orientation into the host nanoporous polymeric crystallites.

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