High Refractive Index Hyperbranched Polymers Prepared by Two Naphthalene‐Bearing Monomers via Thiol‐Yne Reaction

High refractive index (HRI) materials play an important role in optic‐electronic devices. In this study, two compounds with high content of naphthalene groups, 1,5‐dithiolnaphthalene and 1,3,5‐tris(naphthalyl–ethylnyl) benzene, are selected as “A₂” and “B₃” monomers, respectively to prepare hyperbranched HRI polymers. Metal‐free radical‐initiated “A₂ + B₃” thiol‐yne polyaddition is conducted successfully at different monomer molar ratios even for those sterically demanding molecules being able to adjust the molar mass as well as RI. Polymers with refractive index up to 1.79 at 589.7 nm are obtained, which are among the highest RI values so far reported for pure polymer‐based materials. The high RI, based on the high molar refraction of naphthalene group, metal‐free and easy one‐pot synthesis, high transparency in the visible area, good thermal stability, good solubility, and easy processability into thin films, make these polymers excellent candidates for optic‐electronic applications.

     

Selected Polymers that Contain Aromatic Ester Units: Synthesis,Photoreactions, and Refractive Index Modulation

Photoreactive polymers bearing aliphatic and aromatic esters of 4-(N,N-diphenylamino)phenol in the side chain, poly[4-(N,N-diphenylamino)phenyl acrylate] (P1) and poly[4-(N,N-diphenylamino)phenyl 4-vinylbenzoate] (P2), are prepared from their monomers by free radical polymerization. In addition, poly[naphthalene-1-yl 4-vinylbenzoate] is synthesized (P3). These materials absorb UV light up to λ = 350 nm. The polymers P1–P3 as well as low-molecular-weight model compounds are investigated with respect to their photoreactions under UV illumination. It is found that decarboxylation is the dominant reaction and that the photo-Fries rearrangement occurs as a minor reaction. The fully aromatic ester units in P2 are more reactive than the ester units in P1. In the polymers, decarboxylation proceeds more efficiently than in the low-molecular-weight model compounds. Upon UV illumination of the polymers, large increases of the refractive index are observed (Δn₄₅₀ up to +0.07). This is in agreement with the structural changes in the polymers after irradiation as calculated from group contributions to molar refraction. A preliminary investigation under 610 nm fs laser irradiation indicates that refractive index patterns can be produced by two-photon effects (TPA). The polymers are of potential interest for applications in the field of optical waveguides.

     

Novel Inorganic Proton‐Conducting Graft Copolymers Based on 4‐Vinyl Benzene Boronic Acid and Vinyl Phosphonic Acid

As proton‐conducting polymers, phosphonic acid functional polymers are commonly preferred due to their high proton conductivity in humidified and anhydrous systems. In this work, a new copolymer based on 4‐vinyl benzene boronic acid (VBBA) and vinyl phosphonic acid (VPA) is synthesized and then boronic acid groups are grafted with polyethylene glycol methyl ether to produce more‐flexible materials. The reactions are verified by FTIR spectroscopy and thermal analysis (thermogravimetric analysis (TGA) and DSC). The P content of the samples is analyzed by scanning electron microscopy (SEM)–energy dispersive X‐ray spectrometry (EDS). The ion‐exchange capacity (IEC) of the copolymers is measured and compared with the P content. The proton conductivity is investigated in both humidified conditions and the anhydrous state. In 50% humidity, P(VBBA‐co‐VPA)1:0.5 shows a proton conductivity of 5.3 × 10^?3 S cm^?1 at 30 °C.     

Highly Refractive Polyimides Derived from 2,8‐Bis(p‐aminophenylenesulfanyl)dibenzothiophene and Aromatic Dianhydrides

A series of wholly aromatic PIs were prepared from a newly synthesized sulfur‐containing diamine and various aromatic dianhydrides via a two‐step polycondensation procedure. Flexible and tough PI films were cast from their soluble PAA precursors. The PIs showed good thermal stability with 5% weight loss temperatures above 480 °C and glass transition temperatures above 200 °C. The films showed good optical transparency in the visible region with a transmittance above 80% at 500 nm. The linear thioether linkages and the cyclic dibenzothiophene moiety in the PIs endowed the PIs with high refractive indices ranging from 1.7353 to 1.7578 and low birefringence between 0.0068 and 0.0106.

     

Influence of Chemical Structure on the Refractive Index of Imide‐Type Polymers

The influence of different substituents on the optical properties of poly(amide imide)s and polyimides is systematically investigated. All of the polymers exhibit good solubility and film‐forming ability, high thermal stability, and glass transition temperatures of 162–209 °C for poly(amide imide)s and of 209–274 °C for polyimides. The optical transmittance of the films at 450 nm is above 80% for all the studied polyimides and poly(amide imide)s containing benzonitrile units linked in the 2,6‐position. The values of refractive index for poly(amide imide)s are in the range of 1.623–1.748 and for polyimides in the domain of 1.672–1.768.

     

Two-Beam Optical Traps: Refractive Index and Size Measurements of Microscale Objects

A counter-propagating optical trap measurement (COTM) system is proposed and analyzed based on the ray-optics model. In this system, refractive index and size of trapped objects can be estimated by using forward scattered light from the two-beam laser trap with resolution n = 0.013 for the refractive index measurements and 3.3% for the size measurements, which is comparable with current bulk techniques, such as refractometry, and flow cytometry. The unique advantage of the COTM system over conventional approaches lies in its capability of marker-free single-particle characterization in whatever transparent buffer required by living cell, eliminating the necessity of changing the fluid composition of the sample in refractometry, and of tagging target with toxic fluorescence dyes in flow cytometry. Noise analysis predicts a potential improvement in the system resolution by more than two orders of magnitude. This non-invasive and sterile tool complements lab-on-a-chips with single cell manipulation and analysis in living friendly ambient.     

生物组织对四种波长的Ar+激光的折射率及其测量的理论分析

光在生物组织中的传输行为与组织的光学特性有关.折射率是组织光学特性中的一个基本参数.本文从多种理论和多种测量方法中选用菲涅耳公式的理论,引用兔静脉组织在四种波长的Ar 激光作用下的光学特性,推算出兔静脉组织对四种波长的Ar 激光的折射率,分析和讨论了如何在这个理论的基础上完善测量生物组织折射率的技术.     

Refractive Index Changes in Polymers Induced by Deep UV Irradiation and Subsequent Gas Phase Modification

Poly(4‐vinylbenzyl thiocyanate) (PVBT) and a copolymer of styrene and 4‐vinylbenzyl thiocyanate (PST‐co‐VBT) were investigated with regard to changes of the refractive index under UV irradiation (λ = 254 nm). After irradiation, the refractive index n_D of PVBT films increased from 1.629 to 1.660. In the case of the copolymer PST‐co‐VBT, n_D increased from 1.616 to 1.630. The change of the refractive index mainly resulted from the photoinduced isomerization of thiocyanate groups (SCN) to the corresponding isothiocyanates (NCS). The NCS groups formed in the irradiated zones were selectively modified with gaseous amines (ammonia, propylamine, ethylenediamine, and hydrazine) to give thiourea derivatives via an addition reaction. The gas phase modification induced further changes of the refractive index without any loss of the film quality (e. g. propylamine, Δn up to –0.026, and hydrazine, Δn up to +0.035). In addition, the thickness h of the polymer films increased by up to 21% as a result of the gas phase modification. In contrast, wet chemical treatment with bulky amines (1‐methylnaphthylamine, 1‐pyrenemethylamine) caused a considerable deterioration of the film quality. The variation of the refractive index in polymers such as PVBT and PST‐co‐VBT is of potential interest for holographic recordings and the setup of polymer based DFB lasers.     

Relative Contributions of Polarizability and Free Volume in Reduction of Refractive Index and Dielectric Constant with Fluorine Substitution in Polyimides by Positron Annihilation Spectroscopy

Fluorine atom incorporation into polymers typically yields a low refractive index and dielectric constant. Two effects contribute to this: the decreased electronic polarizability of the C–F bond relative to C–H, and the introduction of additional fractional free volume due to less dense polymer chain packing. Here, it is reported that the change in fractional free volume contributes an average of 49% of the observed decrease in refractive index and 64% of the 1 kHz dielectric constant for symmetric structures. This surprisingly large magnitude is found comparing exact fluorine/hydrogen analogous pairs of polyimides using positron annihilation lifetime (PAL) spectroscopy and the application of a Lorenz–Lorentz normalization.

     

Grafting of Poly(2‐Oxazoline) Side Chains from Polyester Containing Oxazoline Units and Their Blends with Water Soluble Vinyl Polymers

Ternary polycondensation of thiomalic acid (TMA), adipic acid (ADA), and 1,5‐pentanediol (PD) at 80 °C proceeds to give polyester having pendent mercapto groups. After the mercapto groups are consumed quantitatively by a Michael addition with 2‐isopropenyl‐2‐oxazoline (IPOx) to create an initiation point for grafting, successive additions of methyl triflate (MeOTf) and 2‐oxazoline allow ring‐opening polymerization of 2‐oxazoline from the IPOx unit to give a graft copolymer with a M_n of 2.2 × 10⁴ ‐ 3.7 × 10⁴ and an molecular dispersity index (M_w/M_n = 1.9–2.6). The synthesized polyester‐based graft copolymer is water‐soluble and forms transparent blend films with poly(vinyl alcohol) (PVA) and poly(N‐isopropy acrylamide) (PNIPAM) using solvent cast methods. Differential scanning calorimetry measurements show that blends with PVA (<30% of the graft copolymer) show a single T_gs over the whole composition range. All scans for the blends with PNIPAM have a single T_gs that is between those of the parent polymers indicating that the graft copolymer shows excellent miscibility with PNIPAM, although the parent polyester, poly(TMA‐alt‐PD)‐co‐poly (ADA‐alt‐PD) does not exhibit such miscibility.     

A Transparent,High Refractive,Shape‐Memory,Healable, and Recyclable Phenolic Polyurethane Thermoset: Unexpected Roles of Bromine Substituents and Tertiary Amine Catalysts

The applications of polyurethane (PU) thermosets are limited by the lack of plasticity after curing due to permanent crosslinks. Besides, the low refractive index is insufficient for optical devices. Here, a transparent, high refractive, recyclable, and healable PU thermoset is developed based on dynamic bromined phenyl‐carbamate bonds (BPCB). It exhibits tensile strength of ≈52 MPa, good shape‐memory ability, and can be reprocessed or healed nearly completely at 110 °C in 30 min. Tertiary amine catalysts and bromine substituents jointly play unexpected roles to promote the forward and reverse reactions significantly, leading to high bond‐exchange efficiency of BPCB. Furthermore, the introducing of BPCB can endow the material with higher refractive index (n_D = 1.5850) simultaneously. In summary, this material is of potential as dynamic PU thermoset in various fields, especially in advanced optical devices.     

Detailed 1D/2D NMR Analyses of Benzophenone‐Related Reaction Products from a Photopolymerization System of Vinyl Acetate and Benzophenone

Summary: A new reaction system was designed in order to allow the reaction between benzophenone (BP) and poly(vinyl acetate) chain/radical or monomer to progress under UV irradiation with relatively constant intensity of absorbed light. After the reaction, most BP‐related products were successfully separated and were directly and particularly studied for the first time by a 600 MHz solution‐state NMR spectrometer. ¹³C, ¹H, DEPT‐135, and 2D ¹H‐¹³C HSQC, ¹H‐¹³C HMBC NMR spectra were utilized for the analyses. In the mixed products, two new structures with new ether groups were detected and confirmed, besides detailed confirmation of benzopinacol and semi‐benzopinacol‐connected poly(vinyl acetate).

Structures 1 and 2