Synthesis, Morphology, and Properties of Polyurethane-triazoles by Click Chemistry

Abstract

To explore the applications of click chemistry in polyurethane materials, a series of novel linear polyurethane-triazoles (PUTs) are prepared using the in situ click reaction of propargylterminated polyurethanes with 1,4-dibromobutane in the presence of sodium azide. The PUT structures are confi rmed by 1 H NMR, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis, and the number-average molecular weights of PUTs range from (3.74-11.16) × 10 4 g mol −1 , determined by gel permeation chromatography. The triazole ring content is characterized and the effects of incorporating the triazole rings on the properties and morphologies of PUTs are examined. Because of the extra dipole-dipole interaction and hydrogen bonds of 1,4-disubstituted triazole in the hard segments, microphase separation of the PUTs is enhanced compared with conventional polyurethane extended with 1,4-butanediol. The tensile strengths of PUTs, from 21.8 to 39.0 MPa, are higher than conventional polytriazole elastomers, owing to the physical crosslinks formed by the hydrogen bonds in the PUTs. However, the thermal stability of the PUTs decreases as the hard segment content increases. regard to health hazards of the isocyanates used, and possible side or unwanted reactions, such as reaction with water or with preformed urethane groups. [6][7][8] Since the copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click reaction" was introduced by Sharpless [ 9 ] and Meldal [ 10 ] independently, it has become a useful tool for connecting polymer fragments to form linear, [11][12][13] star, [14][15][16] and dendrimer architectures, [17][18][19] because of its high effi ciency, regioselectivity and mild reaction conditions. Polymers constructed using regular triazole linkages through click polymerization of small diynes and bisazides, called polytriazoles, are very brittle and show poor processability. [20][21][22] To improve the polymer properties, researchers have inserted polyols, such as PEG [ 23,24 ] and PDMS [ 25,26 ] into the structure to obtain polytriazole elastomers. However, relatively low mechanical properties of these polytriazole elastomers have been observed even after chemical crosslinking. Side chain post-functionalization of PUs by click methodologies has also been reported. PUs with clickable side chain groups, such as

Synthesis of polyurethanes with pendant azide groups attached on the soft segments and the surface modification with mPEG by click chemistry for antifouling applications

“…[17][18][19][20] Taking into account the surface self-enrichment of sosegments of PUs as a result of their higher mobility than hard-segments, polyurethane with pendant azide groups on the so segment (PU-GAP) was prepared rstly in this study to further increase the content of azide groups and improve their surface enrichment. [21][22][23] The azide groups on the so segment afford more reactive agents interacting with antifouling molecules, comparing with the selective modication by the functional groups of the end groups of the polyurethane. 24 As one of widely used indwelling biomaterial, polyurethanes with antifouling or/and anti-bacterial activities have been paid close attention all the time due to intense complications caused by bacteria biolm formation on their surfaces.…”

Polytriazoles based on alkyne terminated polybutadiene with and without urethane segments: Morphology and properties

“…Figure depicts the aggregation of hard domains as bright regions whereas the soft segment matrix as the darker features . The bright regions are much more bigger in PTU compared with PT, implying an enhanced microphase‐separated feature with the synergistic effect of urethane and triazole unit . The aggregation of hard domains as bright regions became smaller after the addition of DOS as plasticizer because it act as a dilute and then the hydrogen bonding interaction between the hard segments and plasticizer induces an decreased degree of microphase separation.…”

“…Interpenetrating polymer network based on polytriazole and polyurethane also showed enhanced mechanical properties . Wang and Ding synthesized linear polyurethane‐triazoles, which even have higher tensile strength and comparable elongation at break when compared with its polyurethane opponent . In fact, the hard domains aggregated by the urethane segments can act as reinforcing filler in the low T g continuous matrix and enhance the mechanical properties of the material …”

Synthesis and Curing of Allyl Urethane NIMMO-THF Copolyether with Three Functional Groups as a Potential Energetic Binder

“…Soft domains mainly affect the elasticity of material at low temperatures. Generally, the inclusion of hard segments into the soft microphase can cause appreciable elevation of the mechanical properties of a material [45,46].…”