A Study on the Kinetics of a Disorder-to-Order Transition Induced by Alkyne/Azide Click Reaction

Abstract

The kinetics of binary blends of poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) diblock copolymer and Rhodamine B azide was investigated during a disorder-to-order transition induced by alkyne/azide click reaction. The change in the domain spacing and conversion of reactants as a function of annealing time were investigated by in situ small-angle X-ray scattering (SAXS) and infrared spectroscopy (IR), suggesting several kinetic processes with different time scales during thermal annealing. While a higher conversion can be realized by extending the annealing time, the microphase-separated morphology is independent of the annealing conditions, as long as both the reagents and final products have enough mobility.

Tailoring block copolymer morphologies via alkyne/azide cycloaddition

“…The conversion of azide at different annealing times was calculated from the integrated area of the azido stretching band at ∼2,100 cm −1 and is plotted in Figure 5. As can be seen, both di‐BCP 10.5‐11‐40 and 10.5‐20.5‐67 showed fast kinetics and high reactivity toward Rhodamine B azide, similar to previous results 35. Conversely, di‐BCP 10.5‐20‐39 showed slower rate at the same temperature, probably due to the much lower concentration of both the alkyne and azide groups.…”

“…The change in chemical structure of the di‐BCP significantly increased the nonfavorable interactions between the two blocks and therefore, drove the di‐BCP into a microphase separated state. In situ small angle X‐ray scattering (SAXS) and infrared (IR) spectroscopy characterizations revealed the fast kinetics of the reaction and subsequent microphase separation 35. Herein, we investigate the morphological transitions induced by the alkyne/azide cycloaddition.…”

Disorder-to-order transitions induced by alkyne/azide click chemistry in diblock copolymer thin films

“…These results indicate that increasing annealing temperature does not lead to significant change in the microphase separated structures, similar to our previous observations in the bulk. 60 We also noted that samples prepared at higher annealing temperatures show higher intensity in the second order peaks. A possible explanation is that increasing annealing temperature improves the sharpness of the interfaces.…”

Thermal stability of ester linkage in the presence of 1,2,3‐Triazole moiety generated by click reaction

“…Esterification is one of the most convenient methods for introducing alkyne or/and azido functional groups at the end of the polymer chain. Therefore, most of the recently reported block copolymers, synthesized by click reaction, have an ester group near TA like PS‐TA‐ES‐Br ( 1 ) . According to the above results, the phase behavior of block copolymers prepared by click reaction could be carefully investigated because equilibrium microdomains are only obtained at high temperatures where pyrolysis of the ester group in the presence of TA could easily occur.…”

“…Since Sharpless and coworkers established copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC), so‐called “click” reaction, in the 1990s, it has been widely employed for organic synthesis due to mild reaction condition, good selectivity, and simplicity . The click reaction is also useful for preparation of block copolymers which cannot be synthesized by conventional polymerization techniques or have complex molecular architectures such as miktoarm or graft geometry. Moreover, a broad spectrum of applications of the click reaction is attributed to high thermal and chemical stability of 1,2,3‐triazole ring (TA) produced by a cycloaddition reaction.…”