Synthesis and characterization of highly refractive polyimides from 4,4′‐thiobis[(p‐phenylenesulfanyl)aniline] and various aromatic tetracarboxylic dianhydrides

An aromatic sulfur‐containing diamine 4,4′‐thiobis[(p‐phenylenesulfanyl) aniline] (3SDA) was synthesized and polymerized with a sulfur‐containing dianhydride 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA) and three nonsulfur aromatic tetracarboxylic dianhydrides, respectively to afford four poly(amic acid)s (PAAs) with the inherent viscosities of 0.54–1.04 dL/g. Flexible and tough polyimide (PI) films obtained from the PAA precursors showed good thermal, mechanical, and optical properties. The glass transition temperatures (T_gs) of the PIs ranged from 179.1–227.2 °C determined by differential scanning calorimetry (DSC), and 173.8–227.3 °C by dynamic mechanical analysis (DMA), depending on the dianhydride used. The 10% weight loss temperatures were in the range of 500–536 °C, showing high intrinsic thermal‐resistant characteristics of the PI films. The PI films also showed good optical transparency above 500 nm, which agreed well with the calculated absorption spectra using the time‐dependent density functional theory. The average refractive indices (n_av) measured at 632.8 nm were 1.7191–1.7482, and the in‐plane/out‐of‐plane birefringences (Δn) were 0.0068–0.0123. The high refractive indices originate from the high sulfur contents, good molecular packing, and the absence of bulky structures. The relatively small birefringence mainly results from the flexible thioether linkages structures of the diamine. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5606–5617, 2007     

High refractive index materials: A structural property comparison of sulfide‐ and sulfoxide‐containing polyamides

High‐refractive‐index polyamides (PAs) are developed by incorporation of sulfide‐ or sulfoxide linkages and chlorine substituents. The PAs are synthesized through the polycondensation of two novel diamine monomers, 2,2′‐sulfide‐bis(4‐chloro‐1‐(4‐aminophenoxy) phenyl ether (3a) and 2,2′‐sulfoxide‐bis(4‐chloro‐1‐(4‐aminophenoxy) phenyl ether (3b), with various aromatic diacids (a–e). The ortho‐sulfide or sulfoxide units, pendant chlorine groups, and flexible ether linkages in the diamine monomers endowed the obtained PAs with excellent solubilities in organic solvents. The resulting PAs showed high thermal stability, with 10% weight loss temperatures exceeding 415 °C under nitrogen and 399 °C in air atmosphere. The combination of chlorine substituents, sulfide or sulfoxide linkages, and ortho‐catenated structures provided polymers with high transparency along with high refractive index values of up to 1.7401 at 632.8 nm and low birefringences (<0.0075). The structure–property relationships of the analogous PAs containing sulfide or sulfoxide linkages were also studied in detail by comparing the results. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2867–2877     

Synthesis of fluorene‐based high performance polymers. I. Poly(arylene thioether)s with excellent solubility and high refractive index

Several poly(arylene thioether)s ( PTEs ) containing a fluorene moiety were synthesized by the polycondensation of masked dithiols such as 9,9‐bis(4‐(N,N‐dimethyl‐S‐carbamoyl)phenyl)fluorene and various difluoroarenes. All PTEs were obtained in quantitative yields. The PTEs showed good thermal stability: the 10% weight loss temperature was over 480 °C under both nitrogen and air atmosphere by TGA, and glass temperature was within a range of 204–275 °C by DSC. Most PTEs exhibited remarkably high refractive index values in a range of 1.66–1.72 at 589 nm, whereas they had a very low degree of birefringence properties. Furthermore, the PTEs showed high solubility in ordinary organic solvents such as chloroform, N‐methylpyrrolidone, and tetrahydrofuran. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3073–3082, 2007     

Synthesis and properties of highly refractive polyimides derived from fluorene‐bridged sulfur‐containing dianhydrides and diamines

Highly refractive and transparent polyimides (PIs) based on fluorene‐bridged and sulfur‐containing monomers have been developed. An aromatic dianhydride, 4,4′‐[p‐thiobis(phenylenesulfanyl)]diphthalic anhydride (3SDEA), was polymerized with several fluorene‐containing diamines, including commercially available 9,9′‐bis(p‐aminophenyl)fluorene (APF), 9,9′‐bis[4‐(p‐aminophenoxy)phenyl]fluorene (OAPF), and newly synthesized 9,9′‐bis[4‐(p‐aminophenyl)sulfanylphenyl]fluorene (ASPF) to afford series A PIs. Meanwhile, series B PIs were obtained from a new dianhydride, 4,4′‐[(9H‐fluorene‐9‐ylidene)bis(p‐phenylsulfanyl)]diphthalic anhydride (FPSP) and two aromatic diamines, ASPF and 4,4′‐thiobis[(p‐phenylenesulfanyl)aniline] (3SDA) via a two‐step polycondensation procedure. The PIs exhibit good thermal stabilities, such as relatively high glass transition temperatures in the range of 220–270 °C and high initial thermal decomposition temperatures (T_10%) exceeding 490 °C. The 9,9′‐disubstituted fluorene moieties endow the PI films with good optical transparency. The optical transmittances of the PI films at 450 nm are all higher than 80% for the thickness of about 10 μm. Furthermore, the highly aromatic fluorene moiety and flexible thioether linkages in the molecular chains of the PIs provide them with high refractive indices of 1.6951–1.7258 and small birefringence of 0.0056–0.0070. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1510–1520, 2008     

Regio‐regular structure high molecular weight poly(propylene carbonate) by rare earth ternary catalyst and Lewis base cocatalyst

Lewis base modification strategy on rare earth ternary catalyst was disclosed to enhance nucleophilic ability of active center during copolymerization of carbon dioxide and propylene oxide (PO), poly(propylene carbonate) (PPC) with H‐T linkages over 83%, and number–average molecular weight (M_n) up to 100 kg/mol was synthesized at room temperature using Y(CCl₃OO)₃‐ZnEt₂‐glycerine catalyst and 1,10‐phenanthroline (PHEN) cocatalyst. Coordination of PHEN with active Zinc center enhanced the nucleophilic ability of the metal carbonate, which became more regio‐specific in attacking carbon in PO, leading to PPC with improved H‐T linkages. Moreover, the binding of PHEN to active Zinc center also raised the carbonate content of PPC to over 99%, whereas the PPC from common rare earth ternary catalyst was about 96%. Unlike the highly regio‐regular structure PPC but with relatively low molecular weight recently reported in the literature, our high molecular weight regio‐regular PPC did show significant improvement in thermal and mechanical performances. PPC with H‐T linkages up to 83.2% showed glass transition temperature (T_g) of 43.3 °C, while T_g of PPC with H‐T linkages of 69.7% was only 36.1 °C. When H‐T connectivity was raised from 69.7 to 83.2%, the modulus of PPC showed a 78% increase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4451–4458, 2008     

Effects of hard‐segment polymers on CO2/N2 gas‐separation properties of poly(ethylene oxide)‐segmented copolymers

Poly(ethylene oxide)‐segmented polyurethanes (PEO‐PUs) and polyamides (PEO‐PAs) were prepared, and their morphology and CO₂/N₂ separation properties were investigated in comparison with those of PEO‐segmented polyimides (PEO‐PIs). The contents of the hard and soft segments in the soft and hard domains, W_HS and W_SH, respectively, were estimated from glass‐transition temperatures with the Fox equation. The phase separation of the PEO domains depended on the kind of hard‐segment polymer; that is, W_HS was in the order PU > PA ≫ PI for a PEO block length (n) of 45–52. The larger W_HS of PUs and PAs was due to hydrogen bonding between the oxygen of PEO and the NH group of urethane or amide. The CO₂/N₂ separation properties depended on the kind of hard‐segment polymer. Compared with PEO‐PIs, PEO‐PUs and PEO‐PA had much smaller CO₂ permeabilities because of much smaller CO₂ diffusion coefficients and somewhat smaller CO₂ solubilities. PEO‐PUs also had a somewhat smaller permselectivity because of a smaller solubility selectivity. This was due to the larger W_HS of PEO‐PUs and PEO‐PAs, that is, a greater contamination of PEO domains with hard urethane and amide units. For PEO‐PIs, with a decrease in n to 23 and 9, W_HS became large and CO₂ permeability decreased significantly, but the permselectivity was still at a high level of more than 50 at 35 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1707–1715, 2000     

Processing polyamides with superheated water

Superheated water (shH₂O) is investigated as a process aid in conventional aliphatic polyamide (PA) systems. The polymers investigated include PA 6 (PA6), PA 6,6 (PA66), PA 6,12 (PA612), and PA 12 (PA12). It is shown that the PA melting and crystallization temperatures are significantly reduced when exposed to shH₂O. For example, the melting temperature of PA6 is depressed from 206 to 153 °C in the presence of shH₂O. A relationship between amide group density and thermal transition temperature reduction is observed. Processing these materials in shH₂O has led to a variety of materials ranging from low‐density foams to higher density locally anisotropic foamed morphologies. In situ observations of PAs melting in the presence of shH₂O are performed using a specially designed reactor. Results from these experiments are used to estimate the diffusion coefficient of shH₂O in PA6. Finally, low‐temperature extrusion is performed with PA6 and shH₂O at temperatures as low as 180 °C and mixture viscosity is estimated. A 20‐fold depression in the melt viscosity of PA6 is observed at 240 °C with shH₂O. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 803–813     

Syntheses and properties of organosoluble polyamides and polyimides based on the diamine 3,3‐bis[4‐(4‐aminophenoxy)‐3‐methylphenyl]phthalide derived from o‐cresolphthalein

Diamine 3,3‐bis[4‐(4‐aminophenoxy)‐3‐methylphenyl]phthalide (BAMP) was derived from the o‐cresolphthalein, and then it was polycondensated with various aromatic dicarboxylic acids and dianhydrides to synthesize polyamides (PAs) and polyimides (PIs), respectively. PAs have inherent viscosities of 0.78–2.24 dL/g. Most of the PAs are readily soluble in a variety of solvents such as DMF, DMAc, and NMP and afforded transparent and tough films from DMAc solutions. The cast films have tensile strengths of 75–113 MPa as well as initial moduli of 1.71–2.97 GPa. These PAs have glass transition temperatures (T_gs) in the range of 242–325°C, 10% weight loss temperatures occur up to 473°C, and char yields are between 57 and 64% at 800°C in nitrogen. PIs were first synthesized to form polyamic acids (PAAs) by a two‐stage procedure that included a ring‐opening reaction, followed by thermal or chemical conversion to polyimides. Inherent viscosities of PAAs are between 0.71 and 1.63 dL/g. Most of the PIs obtained through the chemical cyclodehydration procedure are soluble in NMP, o‐chlorophenol, m‐cresol, etc., and they have inherent viscosities of 0.58–1.32 dL/g. T_gs of these PIs are in the range of 270–305°C and show 10% weight loss temperatures up to 477°C. PIs obtained through the thermal cyclodehydration procedure have tensile strengths of 72–142 MPa, elongations at break of 8–19%, and initial moduli of 1.80–2.72 GPa. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 455–464, 1999     

Poly(arylene thioether)s containing 9,9′‐spirobifluorene moieties in the main chain: Masked dithiol‐based synthesis and excellent optical properties

Poly(arylene thioether)s ( PTEs ) containing 9,9′‐spirobifluorene moieties were synthesized in high yields from 9,9′‐spirobifluorene‐2,2′‐bis(N,N‐dimethylcarbamothioate) 4 as the masked dithiol and various difluoroarenes as electrophilic monomers. All PTEs showed high thermal stability: The 10% weight loss temperature as evaluated by thermogravimetric analysis was over 470 °C under both nitrogen and air atmospheres. The glass transition temperature estimated by DSC was in the range 210–270 °C. The PTEs showed high solubility in ordinary organic solvents, such as CHCl₃, NMP, and THF. Most PTEs exhibited remarkably high refractive indices ranging from 1.69 to 1.73 at 587.6 nm, whereas no or little birefringence was observed for the PTEs . © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4192–4199, 2010     

Initiator efficiency of 2,2′‐azobis(isobutyronitrile) in bulk dodecyl acrylate free‐radical polymerizations over a wide conversion and molecular weight range

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(21) 5559 . The initiator efficiency, f, of 2,2′‐azobis(isobutyronitrile) (AIBN) in dodecyl acrylate (DA) bulk free‐radical polymerizations has been determined over a wide range of monomer conversion in high‐molecular‐weight regimes (M_n ? 10⁶ g mol^?1 [? 4160 units of DA)] with time‐dependent conversion data obtained via online Fourier transform near infrared spectroscopy (FTNIR) at 60 °C. In addition, the required initiator decomposition rate coefficient, k_d, was determined via online UV spectrometry and was found to be 8.4 · 10^?6 s^?1 (±0.5 · 10^?6 s^?1) in dodecane, n‐butyl acetate, and n‐dodecyl acetate at 60 °C. The initiator efficiency at low monomer conversions is relatively low (f = 0.13) and decreases with increasing monomer to polymer conversions. The evolution of f with monomer conversion (in high‐molecular‐weight regimes), x, at 60 °C can be summarized by the following functionality: f^{60 °C} (x) = 0.13–0.22 · x + 0.25 · x² (for x ≤ 0.45). The reported efficiency data are believed to have an error of >50%. The ratio of the initiator efficiency and the average termination rate coefficient, 〈k_t±, (f/〈k_t〉) has been determined at various molecular weights for the generated polydodecyl acrylate (M_n = 1900 g mol^?1 (? 8 units of DA) up to M_n = 36,500 g mol^?1 (? 152 units of DA). The (f/〈k_t〉) data may be indicative of a chain length‐dependent termination rate coefficient decreasing with (average) chain length. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5170–5179, 2004     

Complex amphiphilic networks derived from diamine‐terminated poly(ethylene glycol) and benzylic chloride‐functionalized hyperbranched fluoropolymers

Amphiphilic copolymer networks were prepared from hyperbranched fluoropolymer (HBFP*, M_n = 38 kDa, by atom transfer radical‐self condensing vinyl copolymerization) and linear diamine‐terminated poly(ethylene glycol) (DA‐PEG, M_n = 1,630 Da). Model studies found that the crosslinking mechanism occurred at ambient temperature as a result of reaction between DA‐PEG and the benzylic chlorides of HBFP*. These networks underwent covalent attachment to glass microscope slides derivatized with 3‐aminopropyltriethoxysilane, whereupon gel percent studies at various weight percentages of DA‐PEG to HBFP* found that curing could be achieved at lower temperatures and shortened time periods relative to the previously reported parent HBFP–PEG system. Thermogravimetric analysis revealed that the crosslinked materials gave no evident mass loss up to 250 °C. Differential scanning calorimetry of the complex amphiphilic networks showed a suppressed glass transition temperature, relative to that observed for neat HBFP*, and multiple melting DA‐PEG endotherm(s) near 30 °C. The films possessed a topographically‐complex surface with features that increased in tandem with an increase in the ratio of DA‐PEG to HBFP*, as detected by atomic force microscopy and quantified by increased rms roughness values. Internal reflection infrared imaging revealed a heterogeneous surface composition and confirmed that the domain sizes increased as the weight percent of DA‐PEG increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4782–4794, 2006     

Preparation,characterization, and properties of poly(thioether ether imide)s from isomeric bis(chlorophthalimide)s and 4,4′‐thiobisbenzenethiol

A series of isomeric poly(thioether ether imide)s (PTEIs) containing both thioether and ether linkages were prepared by nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s with 4,4′‐thiobisbenzenethiol. The inherent viscosities of these polymers were in the range of 0.40–0.56 dL/g in m‐cresol at 30°C. The T_g values of PTEIs were 196–236°C; T_5% values reached up to 509–529°C in nitrogen and 508–534°C in air, which indicated this kind of polyimide possessed excellent thermal stability. The hydrolytic stability was arranged in the order: a > b > c > d > e, and improved with increasing the content of 3‐substituted phthalimide unit in the polymer backbone. Flexible films could be cast from the polymer solution with a solid content of 10%. The PTEI films exhibited good mechanical properties with tensile strengths of 90–104 MPa, elongations at break of 6.6–7.9%, and tensile moduli of 2.3–2.6 GPa. The minimum complex viscosity of PTEIs c was about 100 Pa·s at 310°C and the minimum melt viscosity of PTEIs (a–e) decreased with increasing the content of unsymmetrical 3,4′‐substituted phthalimide units. Copyright © 2014 John Wiley & Sons, Ltd.     

Thiourethane‐based thiol‐ene high Tg networks: Preparation,thermal, mechanical,and physical properties

Thiourethane‐based thiol‐ene (TUTE) films were prepared from diisocyanates, tetrafunctional thiols and trienes. The incorporation of thiourethane linkages into the thiol‐ene networks results in TUTE films with high glass transition temperatures. Increases of T_g were achieved by aging at room temperature and annealing the UV cured films at 85 °C. The aged/annealed film with thiol prepared from isophorone diisocyanate and cured with a 10,080‐mJ/cm² radiant exposure had the highest DMA‐based glass transition temperature (108 °C) and a tan δ peak with a full width at half maximum (FWHM) of 22 °C, indicating a very uniform matrix structure. All of the initially prepared TUTE films exhibited good physical and mechanical properties based on pencil hardness, pendulum hardness, impact, and bending tests. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5103–5111, 2007     

Preparation of ABC miktoarm star terpolymer containing poly(ethylene glycol), polystyrene,and poly(tert‐butylacrylate) arms by combining diels–alder reaction,atom transfer radical,and stable free radical polymerization routes

The ABC type miktoarm star terpolymer was prepared utilizing “core‐in” and “core‐out” methods via combination of Diels–Alder reaction (DA), stable free radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, in DA reaction, poly(ethylene glycol)‐maleimide (PEG‐maleimide) precursor was reacted with succinic acid anthracen‐9‐ylmethyl ester 3‐(2‐bromo‐2‐methyl‐propionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yloxy)‐ethoxy‐carbonyl]‐propyl ester, 8 , to give DA adduct, 9 , which has appropriate functional groups for SFRP and ATRP. Second, a previously obtained 9 was used as a macroinitiator for SFRP of styrene at 125 °C. As a third step, this PEG‐polystyrene (PEG‐PSt) precursor with a bromine functionality in the core was employed as a macroinitiator for ATRP of tert‐butylacrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C to give ABC type miktoarm star terpolymer (PEG‐PSt‐PtBA) with controlled molecular weight and low polydispersity (M_w/M_n < 1.27). The obtained polymers were characterized by gel permeation chromatography and ¹H NMR. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 499–509, 2006     

Synthesis,geometric structure,and properties of poly(phenylacetylenes) with bulky para-substituents

Phenylacetylenes (PAs) with bulky substituents (adamantyl, tert-butyl, and n-butyl groups) at the para-position polymerized in good yields with Fe, Rh, Mo, and W catalysts. The formed polymers were soluble, and their number-average molecular weights were in the range of thousands to hundred thousands. Whereas it is known that the poly(PA) obtained with the Fe catalyst is an insoluble cis-cisoidal polymer, the present polymers formed with the same catalyst were totally soluble in many solvents such as benzene and CHCl₃. The ¹H- and ¹³C-NMR and DSC data revealed that both of the polymers formed with the Fe and Rh catalysts had virtually all-cis structures, while those with the Mo and W catalysts had cis-rich and trans-rich structures, respectively. Cis-cisoidal and cis-transoidal structures of para-substituted poly(PAs) could not be distinguished because of their good solubility. The bulky substituents raised the temperature of cis–trans isomerization and improved the thermal stability of the polymers. Poly(p-t-BuPA) showed gas permeability higher than that of poly(PA). © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 3157–3163, 1998     

The synthesis of poly(phenylacetylene)s with bulky chiral silyl groups and the thermal stability of their helical conformation

The polymerization of (−)‐p‐[(tert‐butylmethylphenyl)silyl]phenylacetylene (t‐BuMePhSi*PA) and (+)‐p‐[{methyl(α‐naphthyl)phenyl}silyl]phenylacetylene (MeNpPhSi*PA) with the [(nbd)RhCl]₂ Et₃N catalyst yielded polymers with very high molecular weights over 2 × 10⁶ in high yields. The optical rotations of the formed poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA) were as high as −356 and −150° (c = 0.11 g/dL in CHCl₃), respectively. The circular dichroism (CD) spectrum of poly(t‐BuMePhSi*PA) in CHCl₃ exhibited very large molar ellipticities ([θ]) in the UV region: [θ]_max = 9.2 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −8.0 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The [θ]_max values of poly(MeNpPhSi*PA) were also fairly large: [θ]_max = 7.1 × 10⁴ ° · cm² · dmol⁻¹ at 330 nm and −5.3 × 10⁴ ° · cm² · dmol⁻¹ at 370 nm. The optical rotations of poly(t‐BuMePhSi*PA) and poly(MeNpPhSi*PA), measured in tetrahydrofuran, chloroform, and toluene solutions, were hardly dependent on temperature in the range 22–65 °C. The CD effects of these polymers hardly changed in the temperature range 28–80 °C, either. These results indicate that the helical structures of these polymers are thermally appreciably stable. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 71–77, 2001     

Synthesis and characterization of high nitrile content polyimides as dielectric films for electrical energy storage

Three new isomeric diamines containing three, oxy‐linked benzonitriles (3BCN), one of which is asymmetric (meta, para, or m, p), are synthesized in a 3‐step sequence. Polycondensation of these diamines and four common dianhydrides (6FDA, OPDA, BTDA, and PMDA) in N,N‐dimethylacetamide via poly(amic acid) precursors and thermal curing at temperatures up to 300 °C lead to three series of tough, creasable polyimide (PI) films (tensile moduli = 1.63 ? 2.86 GPa). Among these PIs, two PMDA‐based PIs possess relatively high crystallinity and two OPDA‐based PIs, low crystallinity, whereas all 6FDA‐ and BTDA‐based PIs, and m,m‐3BCN‐OPDA‐PI are amorphous, readily soluble in common polar aprotic solvents. Thermally stable and having high T_g (216 ? 341 °C), these PIs lose 5% weight around 493–503 °C in air and 463–492 °C in nitrogen. Dielectric properties have been evaluated by broadband dielectric spectroscopy (BDS) and electric displacement‐electric‐field (D‐E) loop measurements. D‐E loop results show an increase in high temperature permittivity (at 190 °C/1 kHz) from 2.9 (for parent PI CP2 with no nitrile group) to as high as 4.9 for these PIs, while keeping their dielectric loss relatively low. Thus, an increase in dipole moment density by the presence of three neighboring CN per repeat unit can increase the overall permittivity, which could be further enhanced by sub‐T_g mobility of para‐phenylene linkages (BDS results). Published 2014. J. Polym. Sci., Part A: Polym. Chem. 2014 J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 422–436     

Star polymers by ATRP of styrene and acrylates employing multifunctional initiators

Multifunctional initiators for atom transfer radical polymerization (ATRP) are prepared by converting ditrimethylolpropane with four hydroxyl groups, dipentaerythritol with six hydroxyl groups, and poly(3‐ethyl‐3‐hydroxymethyl‐oxetane) with ～11 hydroxyl groups to the corresponding 2‐bromoisobutyrates or 2‐bromopropionates as obtained by reaction with acid bromides. Star polystyrene (PS) is produced by using these macroinitiators and neat styrene in a controlled manner by ATRP at 110 °C, employing the catalytic system CuBr and bipyridine. M_n up to 51,000 associated with narrow molecular weight distributions (PDI < 1.1) are obtained with conversions up to 32%. Hydrolysis of the star‐PS leads to linear chains having the expected M_n values. The star‐PS polymers based on dipentaerythritol degrade thermally in nitrogen in a two‐step process in which the first low‐temperature step involves scission of the ester linkages and the second step corresponds to the normal PS degradation. Star poly(methyl acrylates) with various cores are likewise prepared in a controlled manner by ATRP of methyl acrylate in bulk and in solution at 60–80 °C with the 1,1,4,7,7‐pentamethyldiethylene triamine ligand. Under these conditions, higher conversions were possible still maintaining low PDI signaling controlled star growth. Multiarm stars of poly(n‐butyl acrylate) and poly(n‐hexyl acrylate) with controlled characteristics have also been prepared. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3748–3759, 2005     

Synthesis of polycarbosilanes by A2 + Bn (n = 2, 3, and 4) type hydrosilylation reaction and evaluation of their refractive index properties

Polycarbosilanes were synthesized by hydrosilylation reaction of A₂ monomer containing bis Si? H moieties and B_n (n = 2, 3, and 4) monomers containing di‐, tri‐, and tetra‐vinyl groups in the presence of Karstedt's catalyst. The corresponding linear polycarbosilanes (LPC) and hyperbranched polycarbosilanes (HBPC) having M_n 2200–51,500 were obtained in 34–94% yield, without any gel product. The values of refractive index (n_D) of the synthesized LPC and HBPC were in the range from 1.460 to 1.711, and were consistent with the structures of the synthesized products. In the case of HBPC, the values of n_D increased with increase of number‐average molecular weight (M_n), molecular weight distribution (M_w/M_n), and glass transition temperature (T_g), apparently because of increased density due to the presence of microgels, that is, high refractive index hyperbranched carbosilanes could be synthesized by A₂ + B_n (n = 3 and 4) method. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Fluorene‐rich high performance polyesters: Synthesis and characterization of 9,9‐fluorenylidene and 2,7‐fluorenylene‐based polyesters with excellent optical property

Polyesters PEs containing high content of fluorene units in their backbones were synthesized from 9,9‐diarene‐substituted fluorene diols ( 1 ) and fluorene‐based diacid chlorides ( 2 ) by high temperature polycondensation at 185 °C in diphenyl ether. The molecular weights of the polyesters PE1‐PE5 were in a range of M_w 25,000–165,000. The polyesters displayed their high thermostability: the glass transition temperatures (T_g) by differential scanning calorimetry analysis ranged from 109 to 217 °C, while the 10% weight loss temperatures (T_d10) measured by thermogravimetric analysis were over 400 °C in nitrogen and 395 °C in air. The polyesters had good solubility in most common organic solvents such as chloroform and toluene and gave tough, transparent and flexible cast films. The transmittance of the films was over 80% in the wavelength range from 450 to 700 nm in any PEs . The PEs exhibited high refractive index values around 1.65, while they had very low degree of birefringence. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2549–2556, 2008