Synthesis and Thermal Characterization of Novel Poly(tetramethylsilanthrylenesiloxane) and Poly(tetramethylsilphenanthrylenesiloxane) Derivatives

Summary Novel poly(tetramethylsilarylenesiloxane) derivatives, i.e. poly(tetramethyl-2,6-silanthrylenesiloxane) (P1), poly(tetramethyl-9,10-silanthrylenesiloxane) (P2), and poly(tetramethyl-1,8-silphenanthrylenesiloxane) (P3), were synthesized by polycondensation of novel disilanol monomers, i.e. 2,6-bis(dimethylhydroxysilyl)-anthracene (M1), 9,10-bis(dimethylhydroxysilyl)anthracene (M2), and 1,8-bis(dimethylhydroxysilyl)phenanthrene (M3), respectively. P1 and P3 were soluble in common organic solvents, such as benzene, toluene, chloroform, dichloromethane, tetrahydrofuran, etc. whereas P2 was almost insoluble in common organic solvents. It was revealed that P1 and P3 were amorphous and that P2 exhibited the crystallinity, as deduced from differential scanning calorimetry (DSC) and X-ray diffraction measurements. The glass transition temperatures (T_g’s) of P1 (118 °C) and P3 (100 °C) were much higher than that of poly(tetramethyl-1,4-silphenylenesiloxane). The temperature at 5% weight loss (T_d5) of P3 was 500 °C, which was higher than those of P1 and P2, and comparable to that of poly(tetramethyl-1,4-silphenylenesiloxane). It would be speculated that the thermostability of the series of poly(tetramethyl-silarylenesiloxane) derivatives is dependent on the stability of arylene moieties incorporated.     

Synthesis and Characterization of Poly(tetramethyl-1,4-silphenylenesiloxane) Derivatives with Oxyethylene Substituent on Phenylene Moiety

Summary Novel poly(tetramethyl-1,4-silphenylenesiloxane) derivatives having 2-methoxy-ethoxy or 2-(2-methoxyethoxy)ethoxy substituents at both 2- and 5-positions on phenylene moieties were synthesized and characterized by differential scanning calorimetry and thermogravimetry analyses. Poly(tetramethyl-1,4-silphenylene-siloxane) derivatives were obtained by condensation polymerization of the corresponding disilanol derivatives, i.e., 1,4-bis(dimethylhydroxysilyl)-2,5-bis(2-methoxyethoxy)benzene and 1,4-bis(dimethylhydroxysilyl)-2,5-bis[2-(2-methoxy-ethoxy)ethoxy]benzene, which were prepared by the Grignard reaction using chlorodimethylsilane and the corresponding dibromobenzene derivatives followed by the hydrolyses, catalyzed by palladium on charcoal. The introduction of 2-methoxyethoxy groups on the phenylene moiety made the melting point high, compared with poly(tetramethyl-1,4-silphenylenesiloxane); however, that of 2-(2-methoxyethoxy)ethoxy groups made it low, indicating the longer oxyethylene moiety induced the lowering of the melting point. There were no significant differences in the thermostabilities of both present polymers, suggesting the length of oxyethylene moiety would not affect the thermostability, though the introduction of polar oxyethylene group onto the phenylene moiety induced a decline of thermostability.     

Synthesis and characterization of poly(tetramethylsilarylenesiloxane) derivatives bearing benzodithiophene moieties

Poly(tetramethylsilarylenesiloxane) derivatives bearing benzo[1,2-b;4,5-b′]dithiophene (P1) and benzo[2,1-b;3,4-b′]dithiophene (P2) moieties were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,6-bis(dimethylhydroxysilyl)benzo[1,2-b;4,5-b′]dithiophene (M1) and 2,7-bis(dimethylhydroxysilyl)benzo[2,1-b;3,4-b′]dithiophene (M2), respectively. It was deduced that P1 is a crystalline polymer while P2 is an amorphous one from the results of differential scanning calorimetry (DSC). Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra when dimethylsilyl substituents were introduced on the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons. The fluorescence quantum yields (Φ_Fs) were not improved by the introduction of dimethylsilyl groups onto the benzo[1,2-b;4,5-b′]dithiophene and benzo[2,1-b;3,4-b′]dithiophene skeletons, whereas the improvement in the Φ_Fs was remarkable in the case of poly(tetramethylsilarylenesiloxane) derivatives that possessed the corresponding fused benzene ring systems, i.e., poly(tetramethyl-2,6-silanthrylenesiloxane) and poly(tetramethyl-1,8-silphenanthrylenesiloxane).     

Synthesis and Thermal Characterization of Novel Fluorene-Based Polysiloxane Derivatives

Three novel poly(tetramethylsilfluorenylenesiloxane) derivatives having different substituent at 9-position of fluorenylene moiety, i.e. dimethyl (P1), spirocyclohexyl (P2), and spirofluorenyl (P3) substituents, were obtained by polycondensation of novel three disilanol monomers, i.e. 2,7-bis(dimethylhydroxysilyl)-9,9-dimethyl- fluorene (M1), 2’,7’-bis(dimethylhydroxysilyl)-spiro(cyclohexane-1,9’-fluorene) (M2), 2,7-bis(dimethylhydroxysilyl)-9,9’-spirobifluorene (M3), respectively. P1–P3 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. It was suggested from the differential scanning calorimetry (DSC) and the X-ray diffraction analysis that P1 exhibited the crystallinity whereas P2 and P3 were amorphous polymers. The glass transition temperature (T _g) determined by DSC and the temperature at 5% weight loss (T _d5) determined by thermogravimetry (TG) were dependent on the substituent at 9-position on fluorene; both orders of T _g and T _d5 were P3 > P2 > P1, indicating the bulkiness of substituent at 9-position of fluorene resulted in the good thermal stability. It is noteworthy that amorphous P3 exhibiting very high T _g of 156 °C and T _d5 of 535 °C is a new heat-resistant polysiloxane derivative as well as a promising candidate for blue-light-emitting materials.     

Synthesis and thermal characterization of novel adamantane-based polysiloxane

Novel polysiloxane derivative having adamantyl moiety in the main chain (P1) was synthesized and characterized by differential scanning calorimetry (DSC), thermogravimetry (TG), and X-ray diffraction analysis. P1 was obtained by bulk polycondensation without catalysts as well as solution polycondensation of novel disilanol monomer, i.e., 1,3-bis[4-(dimethylhydroxysilyl)phenyl]adamantane (M1), which was prepared by the Grignard reaction using chlorodimethylsilane and 1,3-bis(4-bromophenyl)adamantane, followed by the hydrolysis catalyzed by 5% palladium on charcoal. The molecular weight of P1 was dependent on the concentration of M1 in solution polycondensation, and the high concentration of M1 would result in the high average molecular weight of P1. P1 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, and toluene. The glass transition temperature (T_g) of P1 determined from DSC would be dependent on the average molecular weight of P1. The highest T_g was 115 °C and much higher than that of poly(tetramethyl-1,4-silphenylenesiloxane) (−20 °C). The melting temperature (T_m) of P1 seemed to be independent of the average molecular weight of P1 and was in the range of 153-157 °C, which was comparable to the T_m of poly(tetramethyl-1,4-silphenylenesiloxane). The temperature at 5% weight loss (T_d5) of P1 determined by TG was also comparable to that of poly(tetramethyl-1,4-silphenylenesiloxane), indicating that P1 is a new polysiloxane derivative with the high T_g as well as good thermostability.     

Synthesis and characterization of poly(dioxynaphthylene-1,4-dicarbonylnaphthylene)s with various isomeric naphthylene links

Summary Six all-naphthylene polyesters were prepared by the condensation of 1,4-naphthalenedicarboxylic acid (NA) chloride with 1,4-, 1,5-, 1,6-, 2,3-, 2,6-, and 2,7-naphthalenediol (ND) isomers and effects of the isomerism of NDs on structure and properties of the polyesters were investigated.The polymers-1,4,-1,5 and-2,6 with more or less linear ND link were insoluble and the others with bent ND link were soluble in the mixed solvent from phenol/p-chlorophenol/1,1,2,2-tetrachloroethane(TCE). The polymer-2,6 with the most linear ND link did not show a T_g and the highest decomposition initiation temperature(T_D) and T_g's and T_D's of the other polymers were only marginally dependent on their structures.The polymer-2,3 is believed to have a macrocyclic structure consisting of four to six monomer units and the polymer-1,6 is amorphous in its stable chain conformation, while all the other polymers are semicrystalline. The polymers-1,4and-1,5 exhibited an irreversible crystal-to-crystal transition at 380 and 320°C, respectively, whereas the polymer-2,6 a reversible one at 240°C. The polymer-2,7 exhibited an irreversible crystal-to-amorphous transition at 360°C.     

Synthesis and properties of poly(dioxynaphthyleneisophthaloyl)s with various isomeric naphthylene links

Summary By condensation of 1,4-, 1,5-, 1,6-, 2,3-, 2,6-, and 2,7-naphthalenediol (ND) isomers with a isophthaloyl chloride six aromatic polyesters were prepared, and after removal of low molecular weight materials by extraction with acetone their properties were investigated. Effects of the isomerism of the naphthylene units on the properties of the polyesters were discussed. All the polyesters except one derived from 2,7-ND were soluble in a mixed solvent of phenol/p-chlorophenol/1,1,2,2-tetrachloroethane (TCE). Weight-average molecular weight of the polymer derived from 2,3-ND having the lowest inherent viscosity of 0.10 dL/g was measured to be 12,200 g/mol in TCE by means of a laser light scattering spectrometer. Polydispersity of this sample was determined to be 1.59 by a gel permeation chromatography with o-chlorophenol at 100°C. Glass transition temperatures of the polymers ranged from 144 to 195°C, depending on their molecular weight and chain structure. The polyesters derived from 1,6- and 2,3-NDs were amorphous and all the others were crystalline. Melting temperatures (T_m) of the polymers range from 341°C to 417°C and the polymer derived from 2,6-ND showed the highest T_m. All the polymers had initial decomposition temperature higher than 400°C and showed residue more than 50 wt% at 600°C.     

Synthesis and thermal characterization of novel poly(tetramethyl-1,3-silphenylenesiloxane) derivative bearing adamantyl moiety

A novel poly(tetramethyl-1,3-silphenylenesiloxane) derivative having adamantyl moiety, i.e., poly(tetramethyl-5-adamantyl-1,3-silphenylenesiloxane) (P1) was synthesized by solution polycondensation of a novel disilanol monomer, i.e., 1-[3,5-(dimethylhydroxysilyl)phenyl]adamantane (M1). M1 was prepared by the Grignard reaction using chlorodimethylsilane and 1-(3,5-dibromophenyl)adamantane, followed by the hydrolysis catalyzed by 5% palladium on charcoal. P1 exhibited the good solubility in common organic solvents, such as tetrahydrofuran (THF), chloroform, dichloromethane, benzene, and toluene at ambient temperature. P1 was also soluble in hot hexane, diethyl ether, and ethyl acetate. The glass transition temperature (T _g) and temperature at 5% weight loss (T _d5) of P1 were 85 and 517 °C, respectively, and much higher than those of poly(tetramethyl-1,3-silphenylenesiloxane), indicating that P1 is a new polysiloxane derivative with good solubility as well as good thermostability.     

Synthesis and properties of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties

A new monomer, 1,4‐bis(4‐phenoxybenzoyl)naphthalene (BPOBN), was conveniently synthesized via a simple synthetic procedure from readily available materials. A series of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties were prepared by the Friedel‐Crafts acylation solution copolycondensation of terephthaloyl chloride (TPC) with a mixture of BPOBN and 4,4′‐diphenoxybenzophenone (DPOBPN), over a wide range of BPOBN/DPOBPN molar ratios, in the presence of anhydrous AlCl₃ and N‐methylpyrrolidone in 1,2‐dichloroethane. The copolymers with 10–40% BPOBN are semicrystalline and had remarkably increased T_gs over the conventional PEEK and PEKK due to the incorporation of 1,4‐naphthylene moieties in the main chains. The copolymers with 30–40 mol% BPOBN had not only high T_gs of 176–177°C, but also moderate T_ms of 332–338°C, which are suitable for the melt processing. These polymers had tensile strengths of 101.5–104.7 MPa, Young's moduli of 2.49–2.65 GPa, and elongations at break of 13.3–15.7% and exhibited high thermal stability and excellent resistance to organic solvents. POLYM. ENG. SCI., 56:566–572, 2016. © 2016 Society of Plastics Engineers     

Synthesis and optical properties of poly(tetramethylsilarylenesiloxane) derivative bearing diphenylcyclopentadithiophene moiety

The thermal and optical properties of a novel diphenylcyclopentadithiophene-based poly(tetramethylsilarylenesiloxane) derivative (P1), which was prepared via polycondensation of a novel disilanol monomer, i.e., 2,6-bis(dimethylhydroxysilyl)-4,4-diphenylcyclopentadithiophene (M1), were investigated. P1 exhibited good solubility in common organic solvents, such as benzene, toluene, chloroform, dichloromethane and THF at ambient temperature. The glass transition temperature (T_g) of P1 was determined by differential scanning calorimetry to be 109 °C. No melting temperature (T_m) of P1 was observed, indicating the obtained P1 was an amorphous polymer. The temperature at 5% weight loss (T_d5) of P1 was 454 °C, indicating the rather good thermostability of P1. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing dimethylsilyl substituents onto 4,4-diphenylcyclopentadithiophene skeleton. The fluorescence quantum yields (Φ_Fs) of M1 and P1 in chloroform were determined to be 0.36 and 0.39, respectively. It was revealed that M1 and P1 exhibited the higher fluorescence intensity than diphenylcyclopentadithiophene owing to the cooperative effects of the introduction of diphenyl groups onto spiro carbon of cyclopentadithiophene as well as dimethylsilyl moieties onto 2- and 6-position of cyclopentadithiophene skeleton.     

Crystallization kinetics of novel poly(aryl ether ketone) copolymers containing 2,7‐naphthalene moieties

To increase the glass transition temperature (T_g) of poly(aryl ether ketone), and to decrease the melting temperature (T_m) and temperature of processing, a series of novel poly(aryl ether ketone)s with different contents of 2,7‐naphthalene moieties (PANEK) was synthesized. We focused on the influence of the naphthalene contents to the copolymer's crystallization. The crystallization kinetics of the copolymers was studied isothermally and nonisothermally by differential scanning calorimetry. In the study of isothermal crystallization kinetics, the Avrami equation was used to analyze the primary process of the crystallization. The study results of the crystallization of PANEK at cooling/heating rates ranging from 5 to 60°C/min under nonisothermal conditions are also reported. Both the Avrami equation and the modified Avrami–Ozawa equation were used to describe the nonisothermal crystallization kinetics of PANEK. The results show that the increase in the crystallization temperature and the content of 2,7‐naphthalene moieties will make the crystallization rate decrease, while the nucleation mechanism and the crystal growth of PANEK are not influenced by the increasing of the content of 2,7‐naphthalene moieties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2527–2536, 2006     

Chlorosulfonation of poly(2,6-dimethoxy-1,4-phenylene ether)

Chlorosulfonated derivatives of poly(2,6-dimethoxy-1,4-phenylene ether) of varying chlorine content have been synthesized. Demethoxylation and chlorination is shown to occur in the reaction which is proposed to be of free-radical type. Decrease of molecular weight, lowering of the glass transition point (T_g) and thermal degradation temperature (T_d) with increasing chlorine content is indicated to take place during the progress of the reaction.     

Poly(ether ketone azomethane)s and poly(ether ketone imide)s containing naphthylene moieties

A new diamine monomer, 1,5-bis[4-(4-aminophenoxy)]benzoyl-2,6-dimethoxynaphthalene, was synthesized via a Friedel–Crafts acylation reaction followed by an aromatic nucleophilic substitution reaction. Six ether–ketone linked polymers, named as poly(ether ketone azomethane)s and poly(ether ketone imide)s, were successfully prepared through the polycondensations of the diamine monomer with dialdehydes and dianhydrides, respectively. These naphthylated polymers exhibited high T _g values (142–288 °C), due to their bulky and rigid chemical structure. Meanwhile, they showed good thermal stability and improved solubility. Typically, some of them were casted into thin flexible film and showed high moduli.     

Segmented copolymers of uniform tetra-amide units and poly(phenylene oxide): 2. Crystallisation behaviour

The crystallisation behaviour of copolymers of telechelic poly(2,6-dimethyl-1,4-phenylene ether) segments with terephthalic methyl ester endgroups (PPE-2T), 13 wt% crystallisable tetra-amide segments of uniform length units (two-and-a-half repeating unit of nylon-6,T) and dodecanediol (C12) was studied. The crystallisation rate of the T6T6T units was found to be very high despite the high T_g/T_m ratio. The supercooling (T_m−T_c) as measured by DSC is 18 °C at a cooling rate of 20 °C/min. WAXD has elucidated that the tetra-amide units remain organised in the melt.     

Poly(naphthylenethiophene)s and poly(naphthylenevinylenephenylenevinylene)s: effect of naphthalene positional isomers on the light emitting properties of their polymers

Poly(naphthylenethiophene)s and poly(naphthylenevinylene-phenylenevinylene)s prepared from 1,5-dibromo-3,7-di-t-butylnaphthalene showed a significant blue shift in their UV-vis and photoluminescence spectra compared to copolymers derived from the 1,4-naphthylene system, both in solution and in thin film. This is correlated to a change in conjugation effect of the two positional isomers of naphthalene in the polymer backbone, where in 1,4-conjugation an aromatic sextet remains intact in one of the naphthalene rings whereas 1,5-conjugation involves the loss of resonance energy in the entire naphthalene unit. The series of poly(naphthylenevinylene-phenylvinylene)s emitted blue-green light with very high fluorescence quantum yields (80-95%) in solution. A fabricated device showed external quantum efficiency estimated at 0.2-0.4%, with a relatively high turn-on voltage at ∼7.0 V.     

Synthesis and properties of cyclopentadithiophene-based poly(silarylenesiloxane) derivatives

Poly(silarylenesiloxane) derivatives with 4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene moiety, bearing dimethyl- (P1), methylphenyl- (P2) and diphenyl- (P3) substituents on silyl moieties, were prepared via polycondensation of the corresponding disilanol monomers, that is, 2,6-bis(dimethylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M1), 2,6-bis(methylphenylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M2), and 2,6-bis(diphenylhydroxysilyl)-4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene (M3), respectively. P1-P3 exhibited the good solubility in common organic solvents, such as benzene, toluene, chloroform, dichloromethane, THF, and so on. The glass transition temperatures (T_gs) of P1, P2 and P3 were determined by differential scanning calorimetry to be 56, 97 and 137 °C, respectively, depending on the substituent on the silyl moieties. No melting temperatures (T_ms) of P1, P2 and P3 were observed, suggesting the obtained P1-P3 are amorphous polymers. The temperatures at 5% weight loss (T_d5s) of P1, P2 and P3 were 460, 459 and 479 °C, respectively, indicating that the larger number of phenyl group on the silyl moieties resulted in the better thermostability. Bathochromic and hyperchromic effects were observed in the absorption and fluorescence spectra by introducing silyl substituents onto 4,4-dimethylcyclopenta[2,1-b:3,4-b′]dithiophene moiety. In addition, the bathochromic shift of the maximum absorption (λ_abs) and the increase in the fluorescence quantum yield (Φ_F) were observed by the introduction of phenyl group onto the silyl moieties.     

Synthesis and characterization of poly(1,5-naphthylene vinylene) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene)

Poly(1,5-naphthylene vinylene) (PNV) and its copolymers with poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) were synthesized via a liquid-solid two-phase reaction. The liquid phase was a tetrahydrofuran (THF) solution of the monomers, 1,4-bis(bromomethyl)-2-methoxy-5-(2-ethylhexyloxy)benzene (MOEHODCX) and 1,5-bis(bromomethyl) naphthalene (DBMN), and contained a certain amount of tetrabutylammonium bromide (TBAB) as a phase transfer catalyst. The solid phase was potassium hydroxide particles with diameters smaller than 2 mm. The structures of the polymers were studied by infrared and Raman spectroscopies. The solutions of the copolymers emitted green light. The UV-vis and photoluminescence spectral bands of the copolymers showed blue shifts with the increase in their PNV contents. A polymer light-emitting diode was fabricated with the copolymer prepared by copolymerization MOEHODCX and DBMN with feeding molar ratio of 1:1, and its luminescence efficiency was measured to be 0.069.     

Low glass transition temperature aliphatic polyurethanes

Summary The present paper deals with the single step syntheses of a few aliphatic polyurethanes using some simple glycols like ethylene, propylene, 1,3- and 1,4-butylene glycols and two different bis(chloromethyl) compounds viz., 1,4-bis(chloromethyl)-2,5-dimethyl benzene (I), and 1,5-bis(chloromethyl)-2,4-dimethyl benzene (II). The glass transition temperatures, T_g, of these polymers were determined using dilatometric techniques and they ranged from –12 to –48°C. The polyurethanes derived from 1,4-butylene and ethylene glycols were amorphous gums with T_g well below –30°C.     

Synthesis, characterization and photovoltaic properties of random poly(arylene-vinylene)s containing benzothiadiazole

New random poly(arylene-vinylene)s obtained by combining different amounts of benzo[2,1,3]thiadiazole units with 9,9-dialkylfluorene and/or 1,4-dialkoxybenzene building blocks were synthesized by the Suzuki-Heck polymerization and characterized for use in bulk hetero-junction solar cells. Their optical, electrochemical, morphological and photovoltaic features were investigated. Notwithstanding the relatively low weight-average molecular weights of the obtained polymers (7000-13000 Da), they formed good quality films by spin-coating. UV-Vis measurements permitted the evaluation of their band gap (1.77-2.12 eV), enabling them to harvest a broad portion of the solar spectrum from 350 nm to 650-700 nm. An electrochemical study revealed that the copolymers are endowed with HOMO/LUMO energy levels suitable for both an efficient electron transfer and a high open circuit voltage (V_oc) for devices embodying the polymer/PCBM blends. This investigation pinpoints the important role of the copolymer composition (in terms of molar ratio of the monomeric units) on the performance of the donors in BHJs. In fact, in disagreement with the presumed V_oc and current densities, the terpolymer poly[1,4-bis(2-ethylhexyloxy)-2,5-phenylene-vinylene-co-9,9-bis(2-ethylhexyl)-2,7-fluorenylene-vinylene-co-4,7-benzo[2,1,3]thiadiazolylene-vinylene] showed the best performance of the copolymer series, with a PCE of 0.4% and a V_oc of 0.76 V, probably due to the favorable phase separation in the blend and consequently a better exciton dissociation.     

Convenient synthesis of poly(2,6-dihydroxy-1,5-naphthylene) by Cu(II)-amine catalyzed oxidative coupling polymerization

A convenient synthesis of regiocontrolled poly(2,6-dihydroxy-1,5-naphthylene) (PDHN) with high molecular weights by oxidative coupling polymerization of 2,6-dihydroxynaphthalene (2,6-DHN) has been developed. Polymerizations were conducted in 2-methoxyethanol in the presence of di-μ-hydroxo-bis[(N,N,N′,N′-tetramethylethylenediamine)copper (II)] chloride (CuCl(OH)TMEDA) as the catalyst under air at 25 °C. To determine the optimum conditions, the effects of the amounts of the catalysts and the solvents were investigated. In the presence of 5 mol% of the catalyst to the monomer in 2-methoxyethanol, polymerization proceeded smoothly, giving PDHN with a number average molecular weight (M_n) of 52,000. PDHN was converted to poly(2,6-dibutoxy-1,5-naphthylene) (PDBN) to improve the solubility. The structure of PDBN was characterized by ¹H and ¹³C NMR spectroscopy and was estimated to consist completely of the 1,5-linkage. The average refractive indices (n_AV) of the PDHN and PDBN films were 1.6003 and 1.5815, respectively, and the dielectric constants (ε) estimated from the refractive indices were 2.82 and 2.75, respectively.