No abstract

We describe the synthesis of allyl-substituted deoxybenzoin-based aromatic polyesters that combine the advantageous thermal properties of deoxybenzoin with the processability and reactivity of pendent unsaturated groups. A thermally induced Claisen rearrangement of bis-allyl ether-substituted deoxybenzoin 2 produced 3,3′-bis-allyl-4,4′-bishydroxy­deoxybenzoin (BA-BHDB, compound 1) as a novel A2 monomer. BA-BHDB 1 polymerized readily with isophthaloyl chloride to produce a novel set of functional aromatic polyesters. These allyl-substituted polymers exhibited marked solubility advantages over deoxybenzoin-based polymers lacking such pendent groups, affording homogeneous solutions in numerous organic solvents. The processability contributed by the allyl groups afforded access to relatively high molecular weight aromatic polyesters, with estimated number-average molecular weight (M n) values exceeding 20 kDa. Interestingly, evaluation of the thermal properties of these polymers revealed that the pendent allyl groups led to small increases in heat release relative to the unsubstituted deoxybenzoin polymers. Thus, this work represents an advantageous design of nonflammable polymer materials, offering benefits with respect to both processability and heat release properties. Moreover, the utility of these functional deoxybenzoins in post-polymerization cross-linking was demonstrated using multifunctional thiols and thiol–ene reactions.

Novel homopolymers and copolymers containing 2H-benzimidazol-2-one units have been synthesized by N–C coupling reactions of 1H-benzo[d]imidazol-2(3H)-one and activated aromatic dihalides under conditions similar to those for the synthesis of poly(aryl ether)s and poly(benzimidazole sulfone)s. 1H-Benzo[d]imidazol-2(3H)-one behaved like a bisphenol in the polymerization reaction to afford, quantitatively, high molecular weight linear polymers with inherent viscosities (ηinh) ranging from 0.57 to 1.31 dL/g. The polymers were soluble in various organic solvents, and transparent, flexible, and creasable films were cast from its dichloromethane-solution. The homopolymer had a remarkably high glass transition temperature (T g 348 °C) and good thermal stability. Only 30 mol % (8.9 wt %) of the 2H-benzimidazol-2-one unit for the copolymer with 4,4′-biphenol was required to raise the T g of commercial poly(aryl ether), Radel R-5000 from 220 to 269 °C.

Research Question: How important is acute respiratory tract infections in children less than 5 years of age and what are the main factors that need attention. Objective: To determine the magnitude of ARI under 5 years of age in rural areas of Kashmir valley. 2) To identify various risk factors responsible for ARI. Methodology: Community based Cross sectional study using multistage sampling procedure was used to study 1644 children. A house to house survey was carried out in the defined geographical region in order to determine the prevalence and risk factors of ARI less than 5 years of age. Results: Among 1644 children under 5 years of age studied, 886 (53.89%) were males and 758 (46.11%) female. An overall prevalence of 21.41% under 5 years of age was observed in a Kashmir valley. The prevalence of ARI varied according to the age of child being 19.3% in age group of 0-1 years, 23.0% in 1-3 years and 20.4% in age group of 3-5 years. Prevalence of ARI was more (22.5%) in male children as compared to female (20.05%) children [P>0.05]. The socio demographic variables that showed a significant relationship with ARI prevalence were parental literacy status (OR = 1.806; CI = 1.333 -2.447; P < 0.05) and more so the Mother's literacy status (OR = 1.635; CI = 1.284 -2.083; P < 0.05). ARI risk being high among Malnourished children (OR = 2.38; CI = 1.804 -3.157; P<0.05), inappropriately immunized children (OR=2.41; CI = 1.853 -3.154, P<0.05), children lacking exclusive Breast feeding (OR = 4.854; CI = 3.735 -6.309; P< 0.05) or put on early or delayed weaning (OR = 1.66; CI = 1.302 -2.140; P < 0.05). Environmental / housing variables also showed significant association with ARI with risk being high in children living in poor ventilation (OR = 4.865; CI = 3.78 -6.259; P < 0.05), overcrowded houses (OR = 1.829; CI = 1.442 -2.320; P < 0.05), houses with kitchen not separate (OR = 1.829, CI = 1.442 -5.481, P < 0.05), and using cooking fuel other than LPG (OR = 2.063; CI = 1.615-2.634; P < 0.05) Conclusion: Besides sensitizing mothers on childhood nutritional (exclusive breast feeding and early / delayed weaning) and immunization the role of environmental /housing variables (Poor ventilation, over crowding, combined kitchen and use of cooking fuel other than LPG) need attention.

Novel poly(arylene ether) sulfones, sulfoxides, and sulfides containing deoxybenzoin subunits were synthesized by step growth polymerization involving bishydroxydeoxybenzoin (BHDB) and the corresponding sulfur-containing monomers. The isolated polymers demonstrated good solubility in organic solvents, making them easily processible into transparent, flexible, and creasable films upon solution casting. All of the polymers prepared exhibited exceptionally low flammability characteristics, with total heat release (THR) values as low as 6 J/g-K, and char yield values as high as 54%. Integration of deoxybenzoin monomers into polysulfones with 4,4'biphenyl led to heat release capacity (HRC) values less than half that of commercial polysulfones in use today, placing deoxybenzoin-based polysulfones and polysulfoxides into the ultra-low flammability category.Polymer flammability represents a pressing and persistent societal problem of growing importance with increasing global polymer production, consumption, and waste accumulation.[1] The abundance of synthetic polymers in construction, and transportation vehicles places safety concerns, such as flammability, at a high priority. Efforts to overcome the inherent flammability of high volume polymer materials, as well as specialty products, can improve the safety of polymers and reduce the frequency of fire-related catastrophic events. [2]