Cationic polymerization of bis(1-alkylvinyl)benzenes and related monomers, 2. Controlled syntheses of 1,1,3-trimethyl substituted polyindanes

1,1,3-Trimethyl substituted polyindanes were synthesized in the presence of Brønsted acids (H₂SO₄, CF₃COOH) or Lewis acids (BCl₃, AlCl₃) using 1,4-diisopropenylbenzene ( 1 ), 1,4-bis(1-hydroxy-1-methylethyl)benzene ( 2 ) or 1,4-bis(1-chloro-1-methylethyl)benzene ( 3 ) as monomers. The effects of experimental conditions on yields, molar masses and polymer structure were studied in detail with respect to monomer and initiator used, their concentrations, reaction time and experimental procedure. It was shown, that polymerization temperatures above the ceiling temperature and low monomer concentrations favour the formation of indane units. However, in particular the uniformity of the polymer structure is sensitive to the experimental conditions, mainly to the initiator and to the procedure used. DSC measurements on the polymers proved the remarkable heat-resistance of polyindanes (T_dec. ≥ 450°C; T_g ≈ 210°C). The thermal properties were related to the polymer structure and were compared with those of some commercial polymers.     

Management of Chronic Rhinosinusitis in Asthma Patients: Is There Still a Debate?

The united airway concept in which upper and lower respiratory conditions are present in one patient requires special consideration. There is some evidence linking chronic rhinosinusitis and asthma, but a good understanding of the pathophysiology and combined management is still lacking, a fact that leads to discussion. Bronchial asthma is more prevalent in patients who suffer chronic rhinosinusitis. On the other hand, patients with asthma have a greater prevalence of rhinosinusitis than patients without asthma. The effect of chronic rhinosinusitis in patients with or without nasal polyps on asthma treatment, whether medical or surgical, is controversial. Some studies show worsening, other trials improvement, and others no effect. Direct comparisons between surgical and medical treatments are few. Most of the current literature available about this intriguing combination does not provide a good level of evidence. Thus, randomized clinical trials should be performed to better understand the management when asthma and CRS occur together. This review aims to summarize the current state of this association regarding the effects of different types of treatment.