Low dielectric polymers play an important role in replacing traditional inorganic dielectric materials in advanced electronic manufacturing due to their excellent physical and chemical properties. Herein we report the preparation and characterization of two novel low-k dielectric polymers by introducing adamantane into benzocyclobutene. Because the adamantyl group has low polarizability and can increase the free volume of the polymer, both polymers showed low dielectric constants (2.5) and low dielectric loss (o0.001) at the frequency within 10 KHz-5 MHz. They also showed excellent film uniformity and planarity with the surface roughness less than 0.6 nm and good hydrophobicity with the contact angle larger than 1071. Due to the high cross-linked network structure, both of the adamantylbased BCB polymers exhibited high glass transition temperature (4350 1C), high storage modulus and good thermal stability (T d 4 400 1C in nitrogen). Especially, the p-Ada-TVS-BCB polymer showed a low coefficient of thermal expansion (41 mm m À1 1C À1 ). All of these good properties are in accord with the requirement of the interconnect fabrication of Cu metallization using the damascene process. Both of the polymers are suitable for the utilization in the electronic packing industry.
Three novel bismaleimide monomers (MBA-BMI, EBA-BMI, and PBA-BMI) with unsymmetrical backbone and different pendant groups were synthesized using asymmetric diamine and maleic anhydride as the precursors. The prepared bismaleimide monomers show good solubility in common organic solvents such as acetone and tetrahydrofuran. The EBA-BMI melt treated at 180 8C also shows low viscosity about 190-934 mPa s at the temperature range of 160-139 8C below its melting point (166 8C). In addition to the good processability, all three cured bismaleimides show high storage moduli at high temperatures (2.0 GPa at 400 8C), high glass transition temperatures over 400 8C, and good thermal stability with the 5% weight loss temperatures around 470 8C under nitrogen atmosphere.
A series of bismaleimide-triazine resins (EBT) were prepared from 2-(4 0 -maleimido)phenyl-2-(4 0 -maleimidophenoxyl)phenylbutane (EBA-BMI) and 2,2-bis(4-cyanatophenyl)propane (BADCy). The resins show attractive processability with good solubility in low boiling point solvents and wide processing temperature windows. Introduction of diallylbisphenol A (DBA) can decrease the curing temperature of EBT resins that the curing exothermic peak temperature shifted from 291 to 237 8C as the content of DBA increased from 0 to 20%. The curing condition influenced the thermal properties of the cured EBT resins. The glass transition temperature increased as the curing temperature and curing time increased. The cured EBT resins show high glass transition temperature up to 352 8C, high thermal stability with 5% weight loss temperature over 405 8C, low coefficient of thermal expansion about 45 to 52 ppm/8C, and high storage modulus up to 2.6 GPa at 250 8C.
In the present study, benzocyclobutene (BCB) was incorporated into the benzoxazine (BOZ) monomers. BCB-functionalized BOZ monomers were synthesized by the reaction of 4-hydroxybenzocyclobutene, aromatic diamine, and paraformaldehyde in dioxane under reflux. The structure of the monomers was characterized by Fourier transform infrared spectroscopy (FTIR) and proton and carbon nuclear magnetic resonance spectroscopies. The monomers possess two kinds of ring-opening polymerizable functional groups, BCB and BOZ. Differential scanning calorimetry and FTIR were used to study the polymerization behavior of the monomers. Dynamic mechanical analysis demonstrates that the related polymers show high storage moduli maintained in a wide range of temperature up to 300 C and high glass transition temperature at about 330 C. The incorporation of BCB improved the thermal stability and mechanical property of the monomer.
Background. Studies of chronic airway inflammatory diseases have increasingly focused on airway microbiota. However, the microbiota characteristics of asthma and chronic obstructive pulmonary disease (COPD) patients with different airway inflammatory phenotypes remain unclear. Objective. We aimed to reveal the differences of fungal and bacterial microbiota between eosinophilic asthma (EA) and noneosinophilic asthma (NEA) patients and between eosinophilic COPD (EC) and noneosinophilic COPD (NEC) patients. Further, explore whether similarities exist in the airway microbiota of patients with the same phenotype. Methods. Induced sputum samples were collected from 45 asthma subjects and 39 COPD subjects. The airway microbiota of the subjects was profiled by nearly full-length 16S rRNA and internal transcribed space (ITS) sequencing. Results. Subjects with eosinophilic phenotype (EA and EC) showed significant differences in both fungal and bacterial microbiota compared to the corresponding subjects with noneosinophilic phenotype (NEA and NEC). In addition, no differences were observed between the fungal microbiota of subjects with the same phenotype (EA vs. EC, NEA vs. NEC). In bacterial microbiota, the greater relative abundance of Streptococcus thermophilus was observed in EA and EC subjects, while Ochrobactrum was enriched in NEA and NEC subjects. In fungal microbiota, the EA and EC subjects showed higher relative abundances of Aspergillus and Bjerkandera, while the NEA and NEC subjects were enriched in Rhodotorula and Papiliotrema. Conclusions. Different airway inflammatory phenotypes were related to specific fungal and bacterial microbiota in both asthma and COPD, while the same airway inflammatory phenotype revealed a degree of similarity in airway microbiota, particularly in fungal microbiota.
A novel bismaleimide (DOPO-BMI) with unsymmetrical chemical structure and DOPO pendant group has been prepared. The particular molecular structure makes DOPO-BMI show an intrinsic amorphous state with a T g about 1358C and excellent solubility in most organic solvents, which is beneficial to the processability of bismaleimide composite materials. A series of bismaleimide-triazine (BT) resins have been prepared based on DOPO-BMI and 2,2-bis(4-cyanatophenyl)propane at various weight ratios. The prepared BT resins show outstanding solubility in organic solvent and low viscosity about 10-671 mPa s at 1808C. The cured BT resins exhibit high glass transition temperature (T g ) over 3168C. As the weight ratio of DOPO-BMI increases to 80% (BT80), the T g can rise to 3698C (tan d). The cured BT resins also show good thermal stability with the 5% weight loss temperature over 4008C under both nitrogen and air atmosphere.
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