Boosting the Emission Quantum Yield of Urea Cross‐Linked Tripodal Poly(oxypropylene)/Siloxane Hybrids Through the Variation of Catalyst Concentration

Abstract

Transparent monoliths of urea cross-linked tripodal siloxanebased hybrids, named tri-ureasils, were prepared by the solgel process, using a wide concentration range of hydrochloric acid catalyst (1.0 ϫ 10 -3 Յ [HCl] Յ 2.0 M). The gelation time of the monoliths was controlled by varying the amount of water (2.2 and 22.2 mmol) and HCl (between 4.0 ϫ 10 -5 and 8.0 ϫ 10 -2 mmol) incorporated. Their local structure was characterized by X-ray diffraction, 29 Si and 13 C nuclear magnetic 0.05 , and t-U(5000) 0.01 , respectively. The coherence length Eur.

Targeted design leads to tunable photoluminescence from perylene dicarboxdiimide–poly(oxyalkylene)/siloxane hybrids for luminescent solar concentrators

“…A higher HCl concentration was used to induce gelation of this sample, which has previously been shown to affect the proportion of POP/urea aggregates in tri-ureasils. 50 The incorporation of PDI-Sil does not affect the hydrogenbonding interactions in the shorter chain ureasils. However, for PDI-Sil-d-U(4000), an 8% increase in the contribution from ordered, hydrogen-bonded urea-urea aggregates (Peak 3) is observed, at the expense of weaker POP/urea interactions (Peaks 1 and 2).…”

“…Vibrational spectroscopy provides valuable insight into the influence of the preparation method and/or introduction of dopants on the local structure of ureasils. 50,51 In particular, the Amide I region of the FTIR spectrum (1600-1800 cm À1 ) can provide diagnostic information about the specificity and extent of hydrogen bonding interactions associated with the urea linkages (Fig. 3).…”

“…Gaussian deconvolution reveals that 3-5 components are required to model the Amide I band, which is typical of ureasils (see Table S3, ESI †). 50,52 The bands at ca. 1707 (Peak 1), 1660 (Peak 2) and 1635 (Peak 3) cm À1 are common to all samples, and are assigned to stretching vibrations associated with CQO groups located in disordered hydrogen-bonded polyoxyethylene (POE)/polyoxypropylene (POP)-urea associations of increasing strength (Peak 1 and 2), and CQO groups present in significantly more ordered hydrogen-bonded urea-urea aggregates (Peak 3).…”

“…44 The photoluminescence quantum yields (F PL ) of the undoped ureasils determined upon excitation at 350 nm are in good agreement with previously reported values for related di/triureasils (Table 1). 31,50 The magnitude of F PL follows the order d-U(4000) 4 t-U(403) 4 t-U(5000) 4 d-U(600). An increase in the organic polymer chain length for linear di-ureasils has previously been shown to increase the F PL .…”

Effects of thermal treatment on the structure and luminescent properties of Eu 3+ doped SiO 2 –PMMA hybrid nanocomposites prepared by a sol–gel process

“…While the possible applications of lanthanide compounds have grown, the need for new hosts has become even greater [20][21][22]. To the best of our knowledge, there are few papers reporting SiO 2 -PMMA hybrids as new hosts.…”