Carbon nanotube-containing poly(phenylacetylenes) (NT/PPAs) are prepared by in situ polymerizations of phenylacetylene catalyzed by WCl6−Ph4Sn and [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene) in the presence of the nanotubes. The NT/PPAs are characterized by GPC, NMR, UV, FL, TGA, SEM, TEM, and XRD, and it is found that the nanotubes in the NT/PPAs are helically wrapped by the PPA chains. The short nanotubes thickly wrapped in the PPA chains are soluble in common organic solvents including tetrahydrofuran, toluene, chloroform, and 1,4-dioxane. The NT/PPAs are macroscopically processible, and shearing of the NT/PPA solutions readily aligns the nanotubes along the direction of the applied mechanical force. The nanotubes exhibit a strong photostabilization effect, protecting the PPA chains from photodegradation under harsh laser irradiation with incident fluence as high as 10 J/cm2. The NT/PPA solutions effectively limit intense optical pulses, with the saturation fluence tunable by varying the nanotube contents.

Isotactic polystyrene (iPS) is demonstrated to have unique thermal behavior, showing dual reversible crystal melting and irreversible enthalpic relaxation of its rigid amorphous fraction (RAF). Quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC) and standard DSC were used to study the heat capacity of cold-crystallized iPS. IPS shows two or three endotherms depending upon cold crystallization temperature, T c. Crystal melting causes the higher temperature endotherm(s), and under quasi-isothermal conditions, we report for the first time observation of dual locally reversible melting endotherms. Quasi-isothermal TMDSC shows that the RAF is established at the crystallization temperature in iPS. Furthermore, we show that the lowest temperature endothermic peak, called the annealing peak, represents the transition of the RAF. For cold-crystallized iPS the annealing peak is an irreversible, enthalpy-involved relaxation of RAF, which transforms solidlike RAF into liquidlike mobile amorphous fraction. Depending upon T c, RAF may be the sole contributor to the lowest temperature endotherm. To accommodate the relaxation of RAF, the experimentally determined heat capacity should be written in terms of the underlying linear baseline heat capacity plus the enthalpic terms relating to crystal melting and to relaxation of RAF.

The phase structure of crystalline isotactic polystyrene (iPS) has been investigated with temperature-modulated differential scanning calorimetry (TMDSC), wide-angle X-ray scattering (WAXS), and Fourier transform infrared (FTIR) spectroscopy. Quenched amorphous samples have been cold-crystallized at 140 or 170°C for various crystallization times. The degree of crystallinity obtained from WAXS, with the ratio of the crystal peak intensity to the total peak intensity, shows excellent agreement with the crystallinity determined from TMDSC total heat flow endotherms. For the first time, FTIR results show that the absorbance peak ratio (I 981cm Ϫ1/I 1026cm Ϫ1) has a linear correlation with the crystalline mass fraction ( c ) for cold-crystallized iPS according to the following relation: I 981cm Ϫ1/I 1026cm Ϫ1 ϭ 0.54 c ϩ 0.16. This relationship allows the crystallinity of iPS to be determined from infrared spectroscopy analyses in cases in which it is difficult to perform thermal or X-ray measurements. On the basis of the measurements of the heat capacity increment at the glass transition, we find that a significant amount of the rigid amorphous fraction (RAF) coexists with the crystalline and mobile amorphous phases in cold-crystallized iPS. The RAF increases systematically with the crystallization time, and a greater amount is formed at a lower crystallization temperature. A three-phase model (crystalline phase, mobile amorphous phase, and rigid amorphous phase) is, therefore, appropriate for the interpretation of the structure of cold-crystallized iPS. The origin of the low-temperature endothermic peak (annealing peak) has been investigated with TMDSC and FTIR spectroscopy and has been shown to be due to irreversible relaxation of the RAF.

Pyrolysis of hyperbranched poly[1,1‘-ferrocenylene(methyl)silyne] (5) yields mesoporous, conductive, and magnetic ceramics (6). Sintering at high temperatures (1000−1200 °C) under nitrogen and argon converts 5 to 6N and 6A, respectively, in ∼48−62% yields. The ceramization yields of 5 are higher than that (∼36%) of its linear counterpart poly[1,1‘-ferrocenylene(dimethyl)silylene] (1), revealing that the hyperbranched polymer is superior to the linear one as a ceramic precursor. The ceramic products 6 are characterized by SEM, XPS, EDX, XRD, and SQUID. It is found that the ceramics are electrically conductive and possess a mesoporous architecture constructed of tortuously interconnected nanoclusters. The iron contents of 6 estimated by EDX are 36−43%, much higher than that (11%) of the ceramic 2 prepared from the linear precursor 1. The nanocrystals in 6N are mainly α-Fe2O3 whereas those in 6A are mainly Fe3Si. When magnetized by an external field at room temperature, 6A exhibits a high-saturation magnetization (M s ∼ 49 emu/g) and near-zero remanence and coercivity; that is, 6A is an excellent soft ferromagnetic material with an extremely low hysteresis loss.