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First hyperpolarizabilities of dipolar, bis-dipolar, and octupolar molecules
Yang, Si Kyung,Ahn, Hyun Cheol,Jeon, Seung-Joon,Asselberghs, Inge,Clays, Koen,Persoons, André,Cho, Bong Rae Elsevier 2005 Chemical physics letters Vol.403 No.1
<P><B>Abstract</B></P><P>A series of dipolar (<B>1</B>), bis-dipolar (<B>2</B>), and octupolar molecules (<B>3</B>) containing 1, 2, and 6 dipolar units within a molecule has been synthesized and their hyperpolarizabilities were analyzed. The <I>β</I><SUB>HRS</SUB> increases in the order, <B>1</B><<B>2</B><<B>3</B>. The ‘monomeric’ <I>β</I><SUB><I>zzz</I></SUB> increases by approximately twofold from <B>1</B> to <B>2</B>, whereas <I>β</I><SUB><I>zzz</I></SUB> of <B>2</B> and <I>β</I><SUB><I>xxx</I></SUB> of <B>3</B> are similar. Noteworthy is the parallel increase in the hyperpolarizability tensor with the <I>λ</I><SUB>max</SUB>.</P>
Cole, Jacqueline M.,Lin, Tze-Chia,Edwards, Alison J.,Piltz, Ross O.,Depotter, Griet,Clays, Koen,Lee, Seung-Chul,Kwon, O-Pil American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.8
<P>DAST (4-dimethylamino-N-methyl-4-stilbazolium tosylate) is the most commercially successful organic nonlinear optical (NLO) material for frequency-doubling, integrated optics, and THz wave applications. Its success is predicated on its high optical nonlinearity with concurrent sufficient thermal stability. Many chemical derivatives of DAST have therefore been developed to optimize their properties; yet, to date, none have surpassed the overall superiority of DAST for NLO photonic applications. This is perhaps because DAST is an ionic salt wherein its NLO-active cation is influenced by multiple types of subtle intermolecular forces that are hard to quantify, thus, making difficult the molecular engineering of better functioning DAST derivatives. Here, we establish a model parameter, eta(inter), that isolates the influence of intermolecular interactions on second-order optical nonlinearity in DAST and its derivatives, using second-harmonic generation (SHG) as a qualifier; by systematically mapping intercorrelations of all possible pairs of intermolecular interactions to eta(inter), we uncover a relationship between concerted intermolecular interactions and SHG output. This correlation reveals that a sixfold gain in the intrinsic second-order NLO performance of DAST is possible, by eliminating the identified interactions. This prediction offers the first opportunity to systematically design next-generation DAST-based photonic device nanotechnology to realize such a prospect.</P>
Lin, Tze-Chia,Cole, Jacqueline M.,Higginbotham, Andrew P.,Edwards, Alison J.,Piltz, Ross O.,Pé,rez-Moreno, Javier,Seo, Ji-Youn,Lee, Seung-Chul,Clays, Koen,Kwon, O-Pil American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.18
<P>The molecular and supramolecular origins of the superior nonlinear optical (NLO) properties observed in the organic phenolic triene material, OH1 (2-(3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene)malononitrile), are presented. The molecular charge-transfer distribution is topographically mapped, demonstrating that a uniformly delocalized passive electronic medium facilitates the charge-transfer between the phenolic electron donor and the cyano electron acceptors which lie at opposite ends of the molecule. Its ability to act as a “push–pull” π-conjugated molecule is quantified, relative to similar materials, by supporting empirical calculations; these include bond-length alternation and harmonic-oscillator stabilization energy (HOSE) tests. Such tests, together with frontier molecular orbital considerations, reveal that OH1 can exist readily in its aromatic (neutral) or quinoidal (charge-separated) state, thereby overcoming the “nonlinearity-thermal stability trade-off”. The HOSE calculation also reveals a correlation between the quinoidal resonance contribution to the overall structure of OH1 and the UV–vis absorption peak wavelength in the wider family of configurationally locked polyene framework materials. Solid-state tensorial coefficients of the molecular dipole, polarizability, and the first hyperpolarizability for OH1 are derived from the first-, second-, and third-order electronic moments of the experimental charge-density distribution. The overall solid-state molecular dipole moment is compared with those from gas-phase calculations, revealing that crystal field effects are very significant in OH1. The solid-state hyperpolarizability derived from this charge-density study affords good agreement with gas-phase calculations as well as optical measurements based on hyper-Rayleigh scattering (HRS) and electric-field-induced second harmonic (EFISH) generation. This lends support to the further use of charge-density studies to calculate solid-state hyperpolarizability coefficients in other organic NLO materials. Finally, this charge-density study is also employed to provide an advanced classification of hydrogen bonds in OH1, which requires more stringent criteria than those from conventional structure analysis. As a result, only the strongest OH···NC interaction is so classified as a true hydrogen bond. Indeed, it is this electrostatic interaction that influences the molecular charge transfer: the other four, weaker, nonbonded contacts nonetheless affect the crystal packing. Overall, the establishment of these structure–property relationships lays a blueprint for designing further, more NLO efficient, materials in this industrially leading organic family of compounds.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-18/jp400648q/production/images/medium/jp-2013-00648q_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp400648q'>ACS Electronic Supporting Info</A></P>
First hyperpolarizabilities of hexa(ethynyl)benzene derivatives: effect of conjugation length
Piao, Ming Jun,Chajara, Khalil,Yoon, Soo Jung,Kim, Hwan Myung,Jeon, Seung-Joon,Kim, Tae-Hyun,Song, Kai,Asselberghs, Inge,Persoons, André,Clays, Koen,Cho, Bong Rae Royal Society of Chemistry 2006 Journal of materials chemistry Vol.16 No.23
<P>A variety of dipolar and octupolar molecules containing C&z.tbd;C bonds as the conjugation bridge have been synthesized and the linear and nonlinear optical properties (<I>β</I>) were studied. The <I>β(0)</I> value of the dipole increases with conjugation length, whereas that of the octupole decreases from 2a to 2b with concomitant decrease in <I>λ</I><SUB>max</SUB>. A further increase in the conjugation length to 3a–c increased <I>β(0)</I> because of the larger oscillator strength. Moreover, 3a with the most distorted structure shows the largest <I>β(0)</I>, probably because of the dipolar contribution. On the other hand, <I>β<SUB>yyy</SUB></I>/<I>β<SUB>zzz</SUB></I> ratios are smaller than unity, probably because <I>β<SUB>zzz</SUB></I> is overestimated by the errors involved in the resonance correction.</P> <P>Graphic Abstract</P><P>Hexa(ethynyl)benzene derivatives have been synthesized and shown to exhibit a large first hyperpolarizability in the range of <I>β(0)</I> = (90–192) × 10<SUP>−30</SUP> esu; values which are among the largest found in the octupolar molecules measured by the frequency-resolved HRS experiments. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=b601982j'> </P>
Chemical and mechanical modulation of polymeric micelle assembly
Clay, N.,Whittenberg, J.,Leong, J.,Kumar, V.,Chen, J.,Choi, I.,Liamas, E.,Schieferstein, J.,Jeong, J.,Kim, D. Royal Society of Chemistry 2017 Nanoscale Vol.9 No.16
<P>Recently, polymeric micelles self-assembled from amphiphilic polymers have been studied for various industrial and biomedical applications. This nanoparticle self-assembly typically occurs in a solventexchange process. In this process, the quality of the resulting particles is uncontrollably mediated by polymeric solubility and mixing conditions. Here, we hypothesized that improving the solubility of an amphiphilic polymer in an organic solvent via chemical modification while controlling the mixing rate of organic and aqueous phases would enhance control over particle morphology and size. We examined this hypothesis by synthesizing a poly(2-hydroxyethyl) aspartamide (PHEA) grafted with controlled numbers of octadecyl (C18) chains and oligovaline groups (termed 'oligovaline-PHEA-C-18'). The mixing rate of DMF and water was controlled either by microfluidic mixing of laminar DMF and water flows or through turbulent bulk mixing. Interestingly, oligovaline-PHEA-C18 exhibited an increased solubility in DMF compared with PHEA-C18, as demonstrated by an increase of mixing energy. In addition, increasing the mixing rate between water and DMF using the microfluidic mixer resulted in a decrease of the diameter of the resulting polymeric micelles, as compared with the particles formed from a bulk mixing process. Overall, these findings will expand the parameter space available to control particle self-assembly while also serving to improve existing nanoparticle processing techniques.</P>