Synthesis of new photoresponsive polyesters containing norbornadiene residues by the polyaddition of donor–acceptor norbornadiene dicarboxylic acid diglycidyl ester with dicarboxylic acids and their photochemical properties

A donor–acceptor norbornadiene derivative, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid diglycidyl ester (D–A NDGE), was synthesized by the reaction of the cesium salt of 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid with epibromohydrin in N‐methyl‐ pyrrolidone (NMP). The polyaddition reactions of D–A NDGE with certain dicarboxylic acids were carried out with tetrabutylammonium bromide as a catalyst in NMP, producing corresponding polyesters containing D–A norbornadiene (NBD) residues in the main chain in fair to good yields. The photoisomerization of the D–A NBD residues in the polyesters proceeded very smoothly, forming the corresponding quadricyclane groups. The photoreactivities of the D–A NBD residues in the polymer were 50 times higher than those of the NBD residues in the film state and 60 times higher than those in a tetrahydrofuran solution. The stored energy in the quadricyclane groups of the polymers was about 45–55 kJ/mol according to differential scanning calorimetry analysis of the irradiated polymer films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2683–2690, 2001     

Synthesis of self‐photosensitizing polyesters containing donor–acceptor norbornadiene moieties and benzophenone groups and their photochemical reactions

The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007     

Synthesis and photochemical properties of poly(ester–amide)s containing norbornadiene (NBD) residues

N,N′‐Bis[(3‐carboxynorbornadien‐2‐yl)carbonyl]‐N,N′‐diphenylethylenediamine (BNPE) was synthesized in 70% yield by the reaction of 2,5‐norbornadiene‐2,3‐dicarboxylic acid anhydride with N,N′‐diphenylethylenediamine. Other dicarboxylic acid derivatives containing norbornadiene (NBD) residues having N,N′‐disubstituted amide groups were also prepared by the reaction of 2,5‐NBD‐2,3‐dicarboxylic acid anhydride with certain secondary diamines. When the polyaddition of BNPE with bisphenol A diglycidyl ether (BPGE) was carried out using tetrabutylammonium bromide as a catalyst in N‐methyl‐2‐pyrrolidone at 100°C for 12 h, a polymer with number average molecular weight of 69,800 was obtained in 98% yield. Polyadditions of other NBD dicarboxylic acid derivatives containing N,N′‐disubstituted amide groups with BPGE were also performed under the same conditions. The reaction proceeded very smoothly to give the corresponding NBD poly(ester–amide)s in good yields. Photochemical reactions of the obtained polymers with N,N′‐disubstituted amide groups on the NBD residue were examined, and it was found that these polymers were effectively sensitized by adding appropriate photosensitizers such as 4‐(N,N‐dimethylamino)benzophenone and 4,4′‐bis(N,N‐diethylamino)benzophenone in the film state. The stored energies in the quadricyclane groups of the polymers were also evaluated to be about 94 kJ/mol by DSC measurement of the irradiated polymer films. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 917–926, 1999     

Synthesis and photochemical properties of novel pentamethylated norbornadiene containing polyimides

A novel pentamethylated norbornadiene (NBD) based dianhydride, α,α′‐bis‐(3,4,5,6,7‐pentamethylcyclopenta‐2,4‐dienyl)meta‐xylene‐1,2‐dianhydride (3), was prepared from α,α′‐bis‐(pentamethylcyclopentadienyl)meta‐xylene (1) and acetylene dicarboxylic acid. The bis‐adduct formed via Diels–Alder reaction afforded tetra‐acid (2), which was chemically cyclodehydrated to lead the targeted dianhydride (3). New polyimides containing NBD moieties in the main chain were prepared from the dianhydride monomer (3) and various aromatic diamines. The chemical structure of the polymers was confirmed by both ¹H and ¹³C NMR analysis. Their Molecular weights were also measured by SEC. All of these polyimides are soluble at room temperature in common organic solvents, such as chloroform, dichloromethane, THF, DMSO, DMF, and NMP, and show good thermal stabilities. The photochemical isomerization of the NBD into quadricyclane (QC) was investigated by UV/vis spectrophotometry from polymer films using visible sunlight as irradiation source. It was found that the kinetic rate of the conversion NBD‐QC which proceeded smoothly is a first kinetic order. The stored energies released by the transformation of QC groups into NBD ones of the irradiated polymer films were also evaluated by DSC measurement and were found to be around 90 kJ mol^?1. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and photochemical property of polymers with pendant donor–acceptor-type norbornadiene moieties

The donor–acceptor-type norbornadiene (D–A NBD) 1,4,5,6-tetramethyl-3-phenyl-2,5-NBD-2-carboxylic acid was prepared by the Diels–Alder reaction of methyl 3-phenylprop-2-ynoate with 1,2,3,4-tetramethyl-1,3-cyclopentadiene. 1,4,5,6,7-Pentamethyl-3-phenyl-2,5-NBD-2-carboxylic acid was also synthesized in the same way. Styrene-type polymers with pendant D–A NBD moieties were prepared with a 100% degree of substitution (DS) by the reaction of D–A NBD carboxylic acids with poly[(p-chloromethyl)styrene] with 1,8-diazabicyclo[5.4.0]undecene-7 in dimethyl sulfoxide at 70 °C for 6 h. In the reaction of D–A NBD carboxylic acids with poly(2-chloroethyl vinyl ether), the DSs were about 60%. The photochemical valence isomerizations of all the NBD polymers proceeded smoothly with UV irradiation in tetrahydrofuran solutions and in the film state. In addition, the rate of the photochemical reaction of the NBD polymers increased efficiently by the addition of 4,4′-bis(diethylamino)benzophenone as a photosensitizer in a film state. The stored thermal energy of the irradiated polymers was also evaluated by differential scanning calorimetry to be 55–74 kJ/mol. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1764–1773, 2001     

Photoresponsive polyamides containing pentamethylated norbornadiene moieties: Synthesis and photochemical properties under sunlight irradiation

Photoresponsive polyamides containing main‐chain pentamethylated norbornadiene (NBD) moieties are obtained in quantitative yields via the Yamazaki–Higashi reaction between a pentamethylated NBD dicarboxylic acid and a series of aromatic diamines. Chemical structures are confirmed by ¹H and ¹³C NMR and weight average molar masses measured by SEC are in the range of 21,500–28,600 g mol^?1 with chain dispersities close to 2. Physical properties are investigated by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, and viscosimetry. All obtained polyamides are amorphous with glass transition temperatures ranging from 68 to 124 °C. They are soluble at room temperature in common organic solvents and exhibit good thermal stabilities with T_d10 values ranging from 175 to 276 °C. The photochemical isomerization of the NBD moiety into quadricyclane (QC) is studied by UV/vis spectroscopy after sunlight irradiation of polymer films. For all polyamides, a first‐order kinetic rate is observed for the conversion of NBD to QC. The thermal release of the stored energy associated to the reverse transformation of QC groups into NBD ones is about 90–95 kJ mol^?1 as measured by DSC of the irradiated polymer films. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4650–4656     

Copolymerization of carbon monoxide and norbornadiene with a palladium catalyst

Carbon monoxide (CO) and norbornadiene (NBD) with Pd(CH₃CN)₄(BF₄)₂ were copolymerized under various conditions at 50°C. Elemental analysis, infrared spectra, UV, Raman, and NMR spectra showed that the copolymers contained both ketone and unsaturated ring structures. Bidentate nitrogen ligands and phosphorus ligands proved to be more effective at stabilizing catalytic activity than monodentate arsenic ligands or phosphorus ligands. Methanol, protic acid, and an oxidant served as the coinitiator and chain transfer agent, respectively. X-ray diffraction analysis showed the copolymer to be partially crystalline. Thermogravimetric analysis showed that the TG curve for the NBD/CO copolymer has two stages with two maxima peaks at 251 and 470°C. This phenomenon was probably due to increased instability of the copolymers as CO content is increased. Hydrogenation of norbornadiene/CO copolymer with LiAlH₄ and Pd/C in THF yields a hydroxyl-containing polymer and norbornene/CO copolymer, respectively. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1157–1166, 1997     

End‐functionalization of isotactic polypropylene via consecutive chain transfer reaction to norbornadiene and hydrogen

Structurally well‐defined end functionalized isotactic polypropylene (iPP) is prepared by conducting a selective chain transfer reaction during the isospecific polymerization of propylene in the presence of norbornadiene (NBD) and hydrogen using rac‐Me₂Si(2‐Me‐4‐Ph‐Ind)₂ ZrCl₂/MAO as the catalyst. The production of NBD‐capped iPP involves a unique consecutive chain transfer reaction, first to NBD and then to hydrogen, for situating the incorporated NBD at the iPP chain end. The NBD end group of NBD‐capped iPP can be converted into other reactive functional group through functional group transformation reactions. The resulting functional group end‐capped iPP can be used for the construction of stereoregular block copolymers (e.g., iPP‐b‐PMMA and iPP‐b‐PS) through postpolymeriztion reactions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Palladium‐catalyzed three‐component coupling polycondensation of aromatic diiodide,aromatic bis(boronic acid propanediol ester), and norbornadiene: A new route for poly(p‐phenylene vinylene)

A novel synthetic method for soluble precursor polymers of poly(p‐phenylene vinylene) (PPV) derivatives by the palladium‐catalyzed three‐component coupling polycondensation of aromatic diiodides, aromatic bis(boronic acid) derivatives, and norbornadiene is described. For example, the polymerization of 1,4‐diiodo‐2,5‐dioctyloxybenzene, benzene‐1,4‐bis(boronic acid propanediol ester), and norbornadiene at 100 °C for 3 days provided a polymer consisting of the three monomer units in a 97% yield (number‐average molecular weight = 3100, weight‐average molecular weight/number‐average molecular weight = 1.37). A derivative of PPV was produced smoothly by the retro Diels–Alder reaction of the polymer both in a dodecyloxybenzene solution and in a film at 200 °C in vacuo. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3403–3410, 2005     

Charge transfer interactions in polyesters with a donor‐(σ‐bridge)‐acceptor moiety in the repeating unit

Two high molecular weight linear polyesters were investigated to gain insight in how the photophysics of electron donor‐(σ‐spacer)‐electron acceptor (DσA) compounds are affected by incorporation into a polymer. They were prepared by condensation of either adipoyl or sebacoyl chloride with a diol that was functionalized with an N,N‐dialkylaniline donor, a cyclohexyl type σ‐spacer, and a 1,1‐dicyanovinyl acceptor. The solubility, which is very low, and the thermal properties of the polyesters are dictated by physical crosslinking as a consequence of interchain donor‐acceptor interactions. Charge transfer (CT) absorption and emission are observed, which involve CT between DσA moieties of different chains rather than CT processes within a single DσA unit. As a result, the photophysics of the DσA units in the polyesters differs strongly from that of similar DσA compounds in solution. Upon swelling the polymers with THF, the CT fluorescence disappears partly. Analogous polymers containing only an N,N‐dialkylaniline donor display dual fluorescence; one band reflects local emission, while the other is attributed to excimer emission. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4775–4784, 2004     

Polycondensations of dicarboxylic acids and diols derived from optically active amino alcohols

Polycondensations of dicarboxylic acids with diols having amide moieties derived from optically active amino alcohols were carried out. Polymers with M _ns 8,700–17,400 were obtained by the polycondensations using 1.2 eq. of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) in DMF at room temperature for 8 h in satisfactory yields. The T_g of the polymer rose with decrease of the methylene chain length of the dicarboxylic acid. In the T_gs of the polymers from L-leucinol, even-odd effect was observed with increase of the methylene chain length of the dicarboxylic acid. The molecular rotation values of the polymers were constant except for the polymer from succinic acid, which showed the negatively largest one. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2925–2934, 1997     

Cationic polymerization of norbornadiene

The polymerization of norbornadiene (NBD) initiated by the 2‐chloro‐2,4,4‐trimethylpentane/titanium tetrachloride system was investigated. Efforts were made to develop conditions for the living polymerization of NBD by the use of proton trap and electron donor in the ?35 to ?60 °C range however this objective was only partially attained. The molecular weights increased linearly with conversion, and the rate was first‐order in confirmed monomer concentration up to approximately 25%; however, chain transfer became operational beyond this range. The microstructure of polynorbornadiene (PNBD) was investigated by high‐resolution ¹H and ¹³C NMR spectroscopy. According to these techniques, the chain consisted of about equal amounts of exo/exo and exo/endo connected tricyclic repeat units. The head and tail groups were identified and quantitated, and this led to absolute molecular weight determination by integration. Molecular weights obtained by this method and by gel permeation chromatography (relative to polyisobutylene standards) were in good agreement. NMR spectroscopy indicated the presence of small but still identifiable amounts of branching units and their structures. The plot of the glass‐transition temperature against the reciprocal of the number‐average molecular weight was linear and yielded a glass‐transition temperature of 323 °C for the infinite molecular weight polymer. According to thermogravimetric analysis, PNBD was stable up to approximately 250 °C and showed a 5% weight loss at approximately 335 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 732–739, 2003     

Development of functional polymers with cyclic ether moieties. I. Synthesis and properties of polyesters with dioxane moiety in the main chain

A series of novel polyesters containing dioxane moieties in their main chains were synthesized by the bulk polycondensation of trans‐2,5‐bis‐(hydroxy‐ methyl)‐1,4‐dioxane with various aliphatic dicarboxylic acid chlorides. The obtained polyesters, analyzed by differential thermal analysis, possessed crystallinity, the melting point of which exhibited a weak odd–even effect on the methylene unit number and a small decreasing trend with an increase in the methylene unit number. These properties were compared with those of similar polyesters bearing cyclohexane moieties, and it was found that the rigidity of the dioxane moiety plays an important role in enhancing the effective packing of the corresponding polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2536–2542, 2000     

Polyamide–polyester multiblock copolymers by chain‐coupling reactions of carboxy‐terminated polymers with phenylene and pyridylene bisoxazolines

Polyamide–polyester multiblock copolymers were synthesized through the reaction of α,ω‐dicarboxy polyamides and polyesters with various arylene bis(2‐oxazoline)s. 2,2′‐(2,6‐Pyridylene)bis(2‐oxazoline) was very reactive and yielded multiblock copolymers with number‐average molar masses ranging from 15,000 to 25,000 after 30 min of reaction in the bulk at 200 °C. The molar masses and thermal properties of the resulting random multiblock copolymers (glass‐transition temperature, melting temperature, and melting enthalpy) were close to those of their alternating homologues prepared by conventional polycondensation between diamino polyamides and dicarboxy polyesters. This showed that the presence of coupling agent moieties in the polymer chains did not exert a significant influence on the block copolymer morphology. The chain‐coupling method showed several advantages over conventional polycondensation: a much shorter reaction time, a lower temperature, no byproducts, and easy control of the final copolymer properties through the mass ratio of the starting oligomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1331–1341, 2005     

Synthesis and characterization of donor–bridge–acceptor alternating copolymers containing perylene diimide units and their application to photovoltaic cells

We have used Suzuki coupling to prepare a series of alternating copolymers featuring coplanar cyclopentadithiophene and hole‐transporting carbazole units. We observed quenching in the photoluminescence spectra of our polymers after incorporating pendent electron‐deficient perylene diimide ( PDI ) moieties on the side chains, indicating more efficient photoinduced electron transfer. Electrochemical measurements revealed that the PDI ‐containing copolymers displayed reasonable and sufficient offsets of the energy levels of their lowest unoccupied molecular orbitals for efficient charge dissociation. The performance of bulk heterojunction photovoltaic cells incorporating the copolymer/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester blends (1:4, w/w) was optimized when the active layer had a thickness of 70 nm. The photocurrents of the devices were enhanced as a result of the presence of the PDI moieties, thereby leading to improved power conversion efficiencies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1298–1309, 2010     

New polymer syntheses. CIX. Biodegradable,alternating copolyesters of terephthalic acid,aliphatic dicarboxylic acids,and alkane diols

Copolyesters with an alternating sequence of terephthalic acid and aliphatic dicarboxylic acids were prepared with three different methods. First, dicarboxylic acid dichlorides were reacted with bis(2‐hydroxyethyl)terephthalate (BHET) in refluxing 1,2‐dichlorobenzene. Second, the same monomers were polycondensed at 0–20 °C in the presence of pyridine. Third, dicarboxylic acid dichlorides and silylated BHET were polycondensed in bulk. Only this third method gave satisfactory molecular weights. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry revealed that the copolyesters prepared by the pyridine and silyl methods might have contained considerable fractions of cyclic oligoesters and polyesters despite the absence of transesterification and backbiting processes. The alternating sequences and thermal properties were characterized with ¹H NMR spectroscopy and differential scanning calorimetry measurements, respectively. In agreement with the alternating sequence, all copolyesters proved to be crystalline, but the crystallization was extremely slow [slower than that of poly(ethylene terephthalate)]. A second series of alternating copolyesters was prepared by the polycondensation of silylated bis(4‐hydroxybut‐ yl)terephthalate with various aliphatic dicarboxylic acid dichlorides. The resulting copolyesters showed significantly higher rates of crystallization, and the melting temperatures were higher than those of the BHET‐based copolyesters. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3371–3382, 2001     

Cyclic and branched functional polyesters derived from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and various dicarboxylic acids

Triethylamine‐promoted polycondensations of 5,5′,6,6′‐tetrahydroxy‐3,3, 3′,3′‐tetramethyl spirobisindane (TTSBI) and α,ω‐alkane dicarboxylic acid dichlorides were performed with equimolar feed ratios. Three different procedures were compared. At a TTSBI concentration of 0.05 mol/L, gelation was avoided, and soluble cyclic polyesters having two OH groups per repeat unit were isolated. These polyesters were characterized with ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry, and SEC and DSC measurements. All polycondensations with sebacoyl chloride resulted in gelation, regardless of the procedure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1699–1706, 2007     

Microwave‐assisted TCNE/TCNQ addition to poly(thienyleneethynylene) derivative for construction of donor–acceptor chromophores

The alkyne moieties of poly(3‐hexylthienyleneethynylene) were reacted with tetracyanoethylene or 7,7,8,8‐tetracyanoquinodimethane by microwave irradiation to produce donor–acceptor chromophores in the polymer main chain. The resulting polymers were fully characterized by GPC, ¹H NMR, and IR spectroscopies, and elemental analyses. They were both thermally and chemically stable, as revealed by thermogravimetric analyses and ESR measurements. UV–vis‐NIR spectroscopy revealed charge‐transfer bands in the low‐energy region, and electrochemistry confirmed the narrower band gaps with the elevated HOMO and lower LUMO levels relative to the precursor polymer. To take advantage of these postfunctionalization methods, p‐type doping of the polymers with I₂ was attempted. Room temperature conductivities of the postfunctionalized polymers reached 4.5 × 10^?5 S cm^?1, which was about 10 times greater than that of the precursor polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Hyperbranched polyesters based on polycondensation of 1,3,5‐tris(2‐hydroxyethyl) cyanuric acid and 3,5‐dihydroxybenzoic acid

A series of hyperbranched polyesters was produced by the condensation of the monomer 3,5‐dihydroxybenzoic acid with 1,3,5‐tris(2‐hydroxyethyl) cyanuric acid as a trifunctional central core. The monomer‐to‐core ratio was varied between 3 and 45. The resulting polymers were phenolic‐terminated polyesters. The degree of branching of the polyesters was calculated according to the method described by Fréchet and was found to be in the range of 0.7–0.8. The number‐average molecular weights calculated via ¹H NMR spectroscopic degree‐of‐polymerization values are in reasonable agreement with the predicted values derived from the monomer‐to‐core ratio for all prepared polyesters. Thermal and photophysical properties were also studied. Glass‐transition temperatures were determined by differential scanning calorimetry and were found to be relatively independent of the theoretical molar mass. The polyesters were found to be blue emitters, and the solutions exhibited intense fluorescence, with a maximum of 430 nm. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3278–3288, 2005     

New synthetic method for aromatic polyketones from bis(arylsilane)s and aromatic dicarboxylic acid chlorides

A new synthetic method for aromatic polyketones was developed through Friedel–Crafts polycondensation of bis(arylsilane) monomers with aromatic dicarboxylic acid chlorides. The solution polycondensation of these monomer pairs in the presence of aluminum chloride in 1,2‐dichloroethane readily afforded aromatic polyketones having inherent viscosities up to 0.37 dL/g with the elimination of chlorotrimethylsilane. The polycondensation proceeded through aromatic electrophilic ipso substitution, the mechanism of which is very similar to that of normal Friedel–Crafts acylation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2729–2735, 2002