The effect of crosslinking on thermal and mechanical properties of perfluorocyclobutane aromatic ether polymers

As the minimum features in semiconductor devices decrease, it is a new trend to incorporate copper and polymers with dielectric constant less than 3.0 to enhance the performance of the devices. Two fluorinated polymers, poly(biphenyl perfluorocyclobutyl ether) (BPFCB) and poly(1,1,1-triphenyl ethane perfluorocyclobutyl ether) (PFCB), are newly developed polymers with dielectric constants below 3.0. These two polymers have a similar backbone structure, but PFCB has the capability of crosslinking. To know the implications of these two polymers in the semiconductor industry, properties that are important for the integral reliability of Integral Circuits (IC), such as thermal and mechanical properties, should be understood. This comparative study shows that the crosslinking in perfluorocyclobutane aromatic ether polymer can reduce vertical thermal expansion and increase glass transition temperature (T_g) while water absorption, crystalline-like phase, and dielectric constant are slightly increased. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1383–1392, 1998     

Resistive switching polymer materials based on poly(aryl ether)s containing triphenylamine and 1,2,4‐triazole moieties

A series of poly(aryl ether)s were successfully prepared via aromatic nucleophilic substitution reaction from various bisphenols and a novel bipolar aryl difluoride monomer containing electron‐donor triphenylamine and electron‐acceptor 1,2,4‐triazole moieties. The poly(aryl ether)s exhibited excellent solubility in organic solvents such as dimethylformamide, chloroform, and tetrahydrofuran at room temperature. The poly(aryl ether)s showed high thermal stability with T_d10 higher than 500 °C and glass transition temperatures (T_g) higher than 187 °C. The thin films of the poly(aryl ether)s indicated bistable resistive switching behavior with ON/OFF current ratios as high as 10³. The switching on and switching off bias voltages of the poly(aryl ether)s were affected by the bisphenol moiety. The good resistive switching behavior of the poly(aryl ether)s made them promising candidates for future nonvolatile memory applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6861–6871, 2008     

The sulfonation of crosslinked poly(ether ether ketone)—Diffusion‐controlled kinetics

The effect of crosslinks introduced by ion irradiation with 11.7 MeV proton and 30 MeV helium ions on the reactivity of poly(ether‐ether‐ketone) (PEEK) to sulfonation have been investigated following the kinetics of the reaction at room temperature. Concentrated sulfuric acid was used as a swelling and sulfonating agent and the reaction was followed by changes in the FTIR spectrum. The rate of reaction decreased with the degree of crosslinking and the progress with time was consistent with diffusion control of the sulfuric acid into the crosslinked matrix. The results were consistent with the efficiency of the ions in crosslinking PEEK and in particular with the differences in their linear energy transfer (LET). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 775–783, 2009     

Synthesis of multiblock hyperbranched‐linear poly(ether sulfone) copolymers

Hyperbranched poly(ether sulfone) was prepared in the presence of an oligomeric linear poly(ether sulfone) to generate multiblock hyperbranched‐linear (LxHB) copolymers. The LxHB copolymers were prepared in a two‐step, one‐pot synthesis by first polymerizing AB monomer to generate a linear block of a desired molecular weight followed by addition of the AB₂ monomer in a large excess (19:1, AB₂:AB) to generate the hyperbranched block. NMR integration analysis indicates that AB₂:AB ratio is independent of the reaction time. Because the molecular weight still increases with reaction time, these results suggest that polymer growth continues after consumption of monomer by condensation into a multiblock architecture. The LxHB poly(ether sulfone)s have better thermal stability (10% mass loss > 343 vs. 317 °C) and lower T_g (200 vs. > 250 °C) than the hyperbranched homopolymer, higher T_g than the linear homopolymer (<154 °C), while little difference in the solubility character was observed between the two polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4785–4793, 2008     

Perfluorocyclohexenyl aryl ether polymers via polycondensation of decafluorocyclohexene with bisphenols

A novel class of semifluorinated perfluorocyclohexenyl (PFCH) aryl ether homo/copolymers was successfully synthesized with high yield through the step‐growth polymerization of commercially available bisphenols and decafluorocyclohexene in the presence of a triethylamine base. The synthesized polymers exhibit variable thermal properties depending on the functional spacer group (R). PFCH aryl ether copolymers with random and alternating architectures were also prepared from versatile bis‐perfluorocyclohexenyl aryl ether monomers. The PFCH polymers show high thermal stabilities with a 5% decomposition temperature ranging from 359 to 444 °C in air and nitrogen atmosphere. These semifluorinated PFCH aromatic ether polymers contain intact enchained PFCH olefin moieties, making further reactions such as crosslinking and application specific functionalization possible. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 232–238     

Negative‐type photosensitive poly(phenylene ether) based on poly(2,6‐dimethyl‐1,4‐phenylene ether), a crosslinker,and a photoacid generator

A negative‐type photosensitive poly(phenylene ether) (PSPPE) based on poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE), a novel crosslinker 4,4′‐methylene‐bis [2,6‐bis(methoxymethyl)phenol] (MBMP) having good compatibility with PPE, and diphenylidonium 9,10‐dimethoxy anthracene‐2‐sulfonate (DIAS) as a photoacid generator (PAG) has been developed. This resist consisting of PPE (73 wt %), MBMP (20 wt %) and DIAS (7 wt %) showed a high sensitivity (D_0.5) of 58 mJ/cm² and a contrast (γ_0.5) of 9.5 when it was exposed to i‐line (365 nm wavelength light), postexposure baked at 145 °C for 10 min, and developed with toluene at 25 °C. A fine negative image featuring 6 μm line‐and‐space pattern was obtained on the film exposed to 300 mJ/cm² of i‐line by a contact‐printed mode. The resulting polymer film cured at 300 °C for 1 h under nitrogen had a low dielectric constant (ε = 2.46) comparable to that of PPE and a higher T_g than that of PPE. In addition, the cured PSPPE film was pretty low water absorption (<0.05%) as same as PPE. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4949–4958, 2008     

Isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

The isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) are investigated by differential scanning calorimetry over two temperature regions. The Avrami equation describes the primary stage of isothermal crystallization kinetics with the exponent n ≈ 2 for both melt and cold crystallization. With the Hoffman–Weeks method, the equilibrium melting point is estimated to be 406 °C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter (K_g) of the isothermal melt and cold crystallization is estimated. In addition, the K_g value of the isothermal melt crystallization is compared to those of the other poly(aryl ether ketone)s. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1992–1997, 2000     

Facile one‐pot synthesis and thermal cyclopolymerization of aryl bistrifluorovinyl ether monomers bearing reactive pendant groups

A diverse pool of aryl bistrifluorovinyl ether (BTFVE) compounds with reactive pendant groups were prepared in a facile, high yielding three step “one‐pot” synthesis from commercial 4‐bromo(trifluorovinyloxy)benzene. Monomers were confirmed from ATR–FTIR, ¹H, ¹³C, and ¹⁹F NMR, and HRMS analysis. Aryl BTFVE compounds were thermally polymerized to afford perfluorocyclobutyl (PFCB) aryl ether polymers with high number–average molecular weight (M_n) for homopolymers (17,050–27,090) and copolymers with 4,4′‐bis(trifluorovinyloxy)biphenyl monomers (27,860–56,500). The PFCB aryl ether homo‐ and copolymers collectively possess high thermal stability (>299 °C in N₂) and are readily solution processable producing optically transparent films. The thermal polymerization was achieved and reactive moieties remained intact, aside from those functionalized with acrylates. In the case with acrylate functionalized polymers, orthogonal polymerization was achieved by first photopolymerizing the acrylates followed by thermal curing of the aryl trifluorovinyl ether endgroups. Preliminary results in this study produced the successful preparation of photodefinable PFCB aryl ether material. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1887–1893, 2010     

Deprotection‐free preparation of propargyl ether‐containing phosphinated benzoxazine and the structure–property relationship of the resulting thermosets

Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether‐containing benzoxazines. In this study, we report a facile, deprotection‐free preparation of a propargyl ether‐containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH‐containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high‐resolution mass spectrum, ¹H, ¹³C, ¹H‐¹H, ¹H‐¹³C nuclear magnetic resonance (NMR) spectra, and X‐ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring‐opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The T_g of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and T_d 5% (N₂) is 393 °C, respectively, which are higher than those of the homopolymer of (1) . Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Fluorinated poly(arylene ether ketone)s bearing pentafluorostyrene moieties prepared by a modified polycondensation

The polycondensation of decafluorobenzophenone with hexafluorobisphenol A was modified by the addition of a molecular sieve dehydrating apparatus to the refluxing reaction system. This modification promoted the polymerization and enabled the reactions to be conducted in milder conditions and completed in a shorter time, thereby depressing side reactions such as branching and crosslinking. The resulting fluorinated poly(arylene ether ketone)s (FPAEK) were free of gel particles and possessed the designed molecular weights. This modified procedure was also suitable for introducing crosslinkable pentafluorostyrene (FSt) moieties into the polymers at the chain ends and/or inside the chain with the vinyl group of FSt being pendant. The resulting FSt containing fluorinated poly(arylene ether ketone)s (FPAEK‐FSt) can then be thermally crosslinked at 100 °C in the presence of 1% benzoyl peroxide (BPO) or at 250 °C without any initiator. The glass‐transition temperatures (T_g's) of FPAEK increased with increasing molecular weight and leveled off at about 147 °C for the polymer with a number‐average molecular weight of 18,600 Da, whereas the values were not apparently affected by the addition of FSt units. However, crosslinking of the FPAEK‐FSt resulted in an approximate 30 °C increase of the T_g. Spin‐coating FPAEK‐FSt onto silicon wafers followed by crosslinking gave films with excellent thermal stability, physical strength, and adhesion to the substrate as well as good reproducibility in terms of film preparation and optical properties. The refractive index and birefringence of the films measured at a wavelength of 1.55 μm were 1.502 and 2.5 × 10^?3, respectively. © 2002 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4205–4216, 2002     

Synthesis and properties of hyperbranched poly(ether sulfone)s prepared by self‐polycondensation of novel AB2 monomer

Hyperbranched poly(ether sulfone)s were prepared by the self‐polycondensation of the novel AB₂ monomer, 4‐(3,5‐hydroxyphenoxy)‐4′‐fluorodiphenylsulfone. The high‐molecular‐weight polymers were isolated in good yields. The degree of branching (DB) of the resulting polymers was investigated by the preparation of dendritic and linear model compounds. The DB determined by gated decoupling ¹³C NMR measurements was in the range 0.17–0.41 and was dependent on the base used for the self‐polycondensation. It was found that cesium fluoride was an effective base to form the polymer having the DB of 0.41. The resulting hyperbranched poly(ether sulfone)s showed good solubility in organic solvents. The solubility and the glass transition temperature of the polymers were influenced by the terminal functional groups. The unique thermal crosslinking phenomenon was observed during the DSC measurements of the hydroxyl‐terminated hyperbranched poly(ether sulfone) under air condition. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Living cationic polymerization of 2‐adamantyl vinyl ether

Living cationic polymerization of 2‐adamantyl vinyl ether (2‐vinyloxytricyclo[3.3.1.1]^3,7decane; 2‐AdVE) was achieved with the CH₃CH(OiBu)OCOCH₃/ethylaluminum sesquichloride/ethyl acetate [CH₃CH(OiBu)OCOCH₃/Et_1.5AlCl_1.5/CH₃COOEt] initiating system in toluene at 0 °C. The number‐average molecular weights (M_n's) of the obtained poly(2‐AdVE)s increased in direct proportion to monomer conversion and produced the polymers with narrow molecular weight distributions (MWDs) (M_w/M_n = ～1.1). When a second monomer feed was added to the almost polymerized reaction mixture, the added monomer was completely consumed and the M_n's of the polymers showed a direct increase against conversion of the added monomer. Block and statistical copolymerization of 2‐AdVE with n‐butyl vinyl ether (CH₂?CH? O? CH₂ CH₂CH₂CH₃; NBVE) were possible via living process based on the same initiating system to give the corresponding copolymers with narrow MWDs. Grass transition temperature (T_g) and thermal decomposition temperature (T_d) of the poly(2‐AdVE) (e.g., M_n = 22,000, M_w/M_n = 1.17) were 178 and 323 °C, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1629–1637, 2008     

Heat capacity of poly(vinyl methyl ether)

The heat capacity of poly(vinyl methyl ether) (PVME) has been measured using adiabatic calorimetry and temperature‐modulated differential scanning calorimetry (TMDSC). The heat capacity of the solid and liquid states of amorphous PVME is reported from 5 to 360 K. The amorphous PVME has a glass transition at 248 K (?25 °C). Below the glass transition, the low‐temperature, experimental heat capacity of solid PVME is linked to the vibrational molecular motion. It can be approximated by a group vibration spectrum and a skeletal vibration spectrum. The skeletal vibrations were described by a general Tarasov equation with three Debye temperatures Θ₁ = 647 K, Θ₂ = Θ₃ = 70 K, and nine skeletal modes. The calculated and experimental heat capacities agree to better than ±1.8% in the temperature range from 5 to 200 K. The experimental heat capacity of the liquid rubbery state of PVME is represented by C_p(liquid) = 72.36 + 0.136 T in J K^?1 mol^?1 and compared to estimated results from contributions of the same constituent groups of other polymers using the Advanced Thermal AnalysiS (ATHAS) Data Bank. The calculated solid and liquid heat capacities serve as baselines for the quantitative thermal analysis of amorphous PVME with different thermal histories. Also, knowing C_p of the solid and liquid, the integral thermodynamic functions of enthalpy, entropy, and free enthalpy of glassy and amorphous PVME are calculated with help of estimated parameters for the crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2141–2153, 2005     

Poly(aryl ether)s containing o‐terphenyl subunits. II. Random poly(ether sulfone)s

The synthesis of a new A₂X‐type difluoride monomer, N‐2‐pyridyl‐4′,4″‐bis‐(4‐fluorobenzenesulfonyl)‐o‐terphenyl‐3,6‐dimethyl‐4,5‐dicarboxylic imide ( 3 ), is described. The monomer 3 was incorporated into a series of copoly(aryl ether sulfone)s by polymerization of 4,4′‐isopropylidenediphenol and 4,4′‐difluorophenylsulfone. The incorporation of monomer 3 had an observable effect on both the glass‐transition temperature of poly(aryl ether sulfone)s and the tendency for macrocyclic oligomers to form during polymerization. Replacement of the pyridyl imide group via a transimidization reaction with propargyl amine proceeded quantitatively and without polymer degradation. The acetylene containing copoly(aryl ether sulfone) could be crosslinked by simple thermal treatment, resulting in an increase in the glass‐transition temperature and solvent resistance. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 9–17, 2000     

Effect of endgroup modification on dynamic viscoelastic relaxation and motion of hyperbranched poly(ether ketone)s

Fluoro‐terminated hyperbranched poly(ether ketone) (FHPEK) was synthesized and its end groups were modified with alkyl compounds of different chain lengths, i.e., hexyloxy (C6), dodecyloxy (C12), and octadecyloxy, (C18), to produce alkyl‐modified HPEKs (HPEK‐C6, HPEK‐C12, and HPEK‐C18, respectively). Master curves were constructed by using the time‐temperature superposition principle. The horizontal shift factors, a_T, used for the construction of the master curves were fit using the William‐Landel‐Ferry (WLF) equation. From the fitting parameters, the apparent activation energy, E_a, was estimated. With increasing alkyl chain length, the E_a values were found to decrease in the order FHPEK > HPEK‐C6 > HPEK‐C12, and then increase for HPEK‐C18. The average relaxation time, τ_HN, was determined by fitting of the dynamic moduli G′(ω) and G″(ω) to the empirical Havriliak‐Negami equation. Similarly, the τ_HN values decreased in the order of FHPEK > HPEK‐C6 > HPEK‐C12, and then increased for HPEK‐C18. This indicates that the endgroup modification with short alkyl chains (C6, C12) increased the molecular mobility due to the internal plasticization effect of these alkyl chains. Modification with the longer alkyl chain (C18) retarded the molecular motion through an antiplasticization effect caused by summation of nonpolar hydrophobic interactions between long hydrocarbon chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2079–2089, 2008     

Crosslinkable maleimide copolymers for stable NLO properties

Second-order, nonlinear optical polymers based on epoxy-substituted methylvinylisocyanates and N-substituted maleimides were synthesized and characterized with spectral and thermal analysis. The photocrosslinking and thermal-crosslinking reactions of copolymers with different chromophore contents were studied. Thermally induced crosslinking during the poling process, performed at the glass-transition temperature (T_g), was prevented by T_g being decreased through the addition of a plasticizer. Electrooptic coefficients (r₃₃), measured for crosslinked and noncrosslinked systems, had similar absolute values and relaxation dynamics. This behavior was explained in terms of the similar rotational mobility of the chromophore units and the paucity of crosslinking sites. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1589–1595, 2001     

Synthesis and characterization of epoxy functionalized cooligomers based on chlorotrifluoroethylene and allyl glycidyl ether

The synthesis of functionalized fluorocooligomers based on chlorotrifluoroethylene (CTFE) and allyl glycidyl ether (AGE) under radical copolymerization is presented. The compositions of comonomers in the cooligomers were determined by three different analyses viz: from ¹H and ¹⁹F NMR spectroscopy by using 1,3‐bis(trifluoromethyl) benzene as the external standard, epoxy equivalent weight value, and elemental analyses. The compositions determined by three methods were matching reasonably well and showed that the resulting poly(CTFE‐co‐AGE) cooligomers exhibit a tendency for alternation. The distribution of the monomers in the cooligomers was proposed based on the assessment of the reactivity ratios, r_i, of both comonomers. These values were determined from the kinetics of radical copolymerization of CTFE with AGE from Fineman‐Ross, Kelen‐Tudos, and extended Kelen‐Tudos methods which led to the assessment of the average reactivity ratios as: r_CTFE = 0.20 ± 0.03 and r_AGE = 0.15 ± 0.08 at 74 °C. The lower M_n values substantiated the formation of cooligomers rather than copolymers. The formation of cooligomers was attributed to the chain transfer to AGE (by hydrogen abstraction from AGE) from the allylic transfer. The poly(CTFE‐co‐AGE) cooligomers were soluble in most of the common organic polar solvents. An optimization of cooligomer yields was investigated by using ethyl vinyl ether as a third comonomer and from different initiators. The thermal stabilities of the cooligomers, obtained by thermal gravimetric analysis, showed a 5% weight loss at temperatures over 225 °C under air. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3587–3595, 2010     

Lead‐sensitive PNIPAM microgels modified with crown ether groups

A series of lead‐sensitive poly(N‐isopropylacrylamide) microgels with pendant crown ether groups were prepared. Their cation‐sensitive behaviors were studied by dynamic light scattering. When ionic strength is not controlled, adding salts causes the microgel particles to deswell. However, when the salt effect is ruled out by keeping a constant ionic strength, adding Pb²⁺ results in much larger swelling. The Pb²⁺‐induced swelling was explained by the formation of host–guest complex between Pb²⁺ and the pendant crown ether groups, which increases the hydrophilicity of the polymer and accordingly the degree of swelling. The lead sensitivity of the microgels increases with increasing crown ether content. For the modified microgel with the highest crown ether content, it swells to ～430% of its original volume at [Pb²⁺] = 10 mM. Other cations also increase the swelling degree of the modified microgels. The extent of the cation‐induced swelling mainly depends on their affinity to the pendant crown ether groups. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4120–4127, 2010     

Analysis of crystallization kinetics of poly(ether ether ketone)

An optical microscope equipped with a video photograph system was used to follow the growth of spherulites. Under nitrogen atmosphere, the growth rates at 290 and 300°C suggest that when the melt of PEEK has been equilibrated for 15 min at 400°C, the subsequent crystallization behavior was nearly independent of the prior thermal history. Linear growth rates of crystallization of PEEK have been measuredin the temperature range of 260–325°C for melt-pressed films and solvent cast films. Detailed kinetic analysis indicated that PEEK exhibited an unmistakable regime II → III transition at 296 ± 1°C. The II → III transition was clearly present irrespective of the rather drastic changes in U*. It is interesting that the branching and crosslinking retarded the growth rate of PEEK, but a transition from regime II to regime III still existed. For melt-pressed films after equilibration at 400°C for 15 min, values of σ and q suggest that U* should be taken nearer to 1500 cal/mol in the case of T_∞ = T_g − 30 K and 2000 cal/mol in the case of T_∞ = T_g − 51.6 K. The K_g(III)/K_g(II) ratio (1.32) was not as close to the predicted value of 2 as was Hoffman's ratio. For PEEK, the Thomas-Staveley constant (β) should be closer to 0.25 or 0.3 instead of 0.1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1335–1348, 1998     

Radical copolymerization behavior of a highly fluorinated cyclic olefin with vinyl ether

The copolymerization of a highly fluorinated cyclic monomer, octafluorocyclopentene (OFCPE, M₁), with ethyl vinyl ether (EVE, M₂) was investigated with a radical initiator in bulk. Despite the poor homopolymerizability of each monomer, the copolymerization proceeded successfully, and the molecular weights of the copolymers reached up to more than 10,000. Incorporation of the OFCPE units into the copolymer led to an increase in the glass‐transition point. The copolymer composition was determined from ¹H NMR spectra and elemental analysis data. The molar fraction of the OFCPE unit in the copolymer increased and approached but did not exceed 0.5. The monomer reactivity ratios were estimated by the Yamada–Itahashi–Otsu nonlinear least‐squares procedure as r_1,OFCPE = ?0.008 ± 0.010 and r_2,EVE = 0.192 ± 0.015. The reactivity ratios clearly suggest that the copolymerization proceeds alternatively in the case of an excessive feed of OFCPE. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1151–1156, 2002