An official website of the United States government
A highly efficient metal-free protocol for the synthesis of linear polydicyclopentadiene
We have developed a highly efficient synthesis of linear polydicyclopentadiene (pDCPD)viaphotoredox mediated metal-free ring-opening metathesis polymerization (MF-ROMP) and investigated theTg–Mndependence of linear pDCPD.
more »
« less
- Award ID(s):
- 2002886
- PAR ID:
- 10472666
- Publisher / Repository:
- Polymer Chemistry
- Date Published:
- Journal Name:
- Polymer Chemistry
- Volume:
- 12
- Issue:
- 19
- ISSN:
- 1759-9954
- Page Range / eLocation ID:
- 2860 to 2867
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract The solid‐state foaming process produces microcellular foams with an outer layer of solid skin that encapsulates the cellular core. In this article, we implement a 1D model to predict the thickness of the solid skin based on the effectiveTgof the polymer‐gas system for a given foaming temperature. The model is based on the understanding that bubbles nucleate when the foaming temperature exceeds the effectiveTgduring the foaming process. The model was validated with experimental results on the PC‐CO2system, which showed that skin thickness decreases with increased foaming temperature. We also developed a linear correlation to accurately predict effectiveTgat different CO2concentrations. The article also explores the model sensitivity to the key input parameters related to gas diffusion. HighlightsLinear correlation to accurately predict effectiveTgprofiles in PC‐CO2system.Increasing foaming temperature decreases skin thickness.Model is sensitive to the input parameters related to gas diffusion.more » « less
-
Abstract Discovery of new materials with enhanced optical properties in the visible and UV‐C range can impact applications in lasers, nonlinear optics, and quantum optics. Here, the optical floating zone growth of a family of rare earth borates,RBa3(B3O6)3(R= Nd, Sm, Tb, Dy, and Er), with promising linear and nonlinear optical (NLO) properties is reported. Although previously identified to be centrosymmetric, the X‐ray analysis combined with optical second harmonic generation (SHG) assigns the noncentrosymmetricPspace group to these crystals. Characterization of linear optical properties reveals a direct bandgap of ≈5.61–5.72 eV and strong photoluminescence in both the visible and mid‐IR regions. Anisotropic linear and nonlinear optical characterization reveals both Type‐I and Type‐II SHG phase matchability, with the highest effective phase‐matched SHG coefficient of 1.2 pm V−1at 800‐nm fundamental wavelength (for DyBa3(B3O6)3), comparable to β‐BaB2O4(phase‐matchedd22≈ 1.9 pm V−1). Laser‐induced surface damage threshold for these environmentally stable crystals is 650–900 GW cm−2, which is four to five times higher than that of β‐BaB2O4, thus providing an opportunity to pump with significantly higher power to generate about six to seven times stronger SHG light. Since the SHG arises from disorder on the Ba‐site, significantly larger SHG coefficients may be realized by “poling” the crystals to align the Ba displacements. These properties motivate further development of this crystal family for laser and wide bandgap NLO applications.more » « less
-
Aims.We cross-correlated galaxies from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) second data release (DR2) radio source with the extended Baryon Oscillation Spectroscopic Survey (eBOSS) luminous red galaxy (LRG) sample to extract the baryon acoustic oscillation (BAO) signal and constrain the linear clustering bias of radio sources in LoTSS DR2. Methods.In the LoTSS DR2 catalogue, employing a flux density limit of 1.5 mJy at the central LoTSS frequency of 144 MHz and a signal-to-noise ratio (S/N) of 7.5, additionally considering eBOSS LRGs with redshifts between 0.6 and 1, we measured both the angular LoTSS-eBOSS cross-power spectrum and the angular eBOSS auto-power spectrum. These measurements were performed across various eBOSS redshift tomographic bins with a width of Δz = 0.06. By marginalising over the broadband shape of the angular power spectra, we searched for a BAO signal in cross-correlation with radio galaxies, and determine the linear clustering bias of LoTSS radio sources for a constant-bias and an evolving-bias model. Results.Using the cross-correlation, we measured the isotropic BAO dilation parameter asα = 1.01 ± 0.11 atzeff = 0.63. By combining four redshift slices atzeff = 0.63, 0.69, 0.75, and 0.81, we determined a more constrained value ofα = 0.968−0.095+0.060. For the entire redshift range ofzeff = 0.715, we measuredbC = 2.64 ± 0.20 for the constant-bias model,b(z0) =bC, and thenbD = 1.80 ± 0.13 for the evolving-bias model,b(z) =bD/D(z), withD(z) denoting the growth rate of linear structures. Additionally, we measured the clustering bias for individual redshift bins. Conclusions.We detected the cross-correlation of LoTSS radio sources and eBOSS LRGs at a 9.2σstatistical significance for one single redshift bin and at a 14.7σsignificance when the four redshift bins were combined. For the BAO signal, we achieved a significance of 2.2σfor a single redshift bin, 2.7σfor the combined cross-correlation and eBOSS auto-correlation, and 4σfor the combined analysis of four redshift bins in the cross-correlation, when assuming a Gaussian distribution for the BAO dilation parameter.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1PY00191D
