Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials.Although NTE behaviors have been found in kinds of compounds,it remains challeng...Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials.Although NTE behaviors have been found in kinds of compounds,it remains challenging for polymers to achieve intrinsic NTE property.In this work,we systematically studied the conformational change of dibenzocyclooctadiene(DBCOD) derivatives between chair(C) and twist-boat(TB) forms based on density-functional theo ry(DFT) calculations,and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related polymers.In order to obtain the polymer with NTE property,two conditions should be met for the thermal contracting DBCOD related units as follows:(i) the TB conformation can turn into C conformation as the temperature increases,and(ii) the volume of C conformation is smaller than that of TB conformation.This rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.展开更多
A novel diamine monomer 2H-(4-aminophenyl)-4-[4-(4-aminophenoxy) biphenyl]phthalazinone 1 containing aza hetero cycle was synthesized and utilized for preparation of new high molecular weight aromatic polyamides with ...A novel diamine monomer 2H-(4-aminophenyl)-4-[4-(4-aminophenoxy) biphenyl]phthalazinone 1 containing aza hetero cycle was synthesized and utilized for preparation of new high molecular weight aromatic polyamides with various aromatic dicarboxylic acids with the inherent viscosity of 0.50 similar to 1.62 g/dL. These polyamides had rather high glass transition temperatures of 327 similar to 356 degreesC and their structure was confirmed by IR, H-1 NMR and MS. They are readily soluble in polar solvents such as NMP, DMF etc, and easily cast into tough, flexible films.展开更多
基金supported by the National Natural Science Foundation of China (Nos.51633001,51721002 and 51873040)National Key R&D Program of China (No.2016YFC1100300)。
文摘Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials.Although NTE behaviors have been found in kinds of compounds,it remains challenging for polymers to achieve intrinsic NTE property.In this work,we systematically studied the conformational change of dibenzocyclooctadiene(DBCOD) derivatives between chair(C) and twist-boat(TB) forms based on density-functional theo ry(DFT) calculations,and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related polymers.In order to obtain the polymer with NTE property,two conditions should be met for the thermal contracting DBCOD related units as follows:(i) the TB conformation can turn into C conformation as the temperature increases,and(ii) the volume of C conformation is smaller than that of TB conformation.This rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.
文摘A novel diamine monomer 2H-(4-aminophenyl)-4-[4-(4-aminophenoxy) biphenyl]phthalazinone 1 containing aza hetero cycle was synthesized and utilized for preparation of new high molecular weight aromatic polyamides with various aromatic dicarboxylic acids with the inherent viscosity of 0.50 similar to 1.62 g/dL. These polyamides had rather high glass transition temperatures of 327 similar to 356 degreesC and their structure was confirmed by IR, H-1 NMR and MS. They are readily soluble in polar solvents such as NMP, DMF etc, and easily cast into tough, flexible films.
