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455_ftp High-Tg Transparent Poly on Phosphinated Bisphe , Introduction Bisphenols, such as bisphenol A or bisphenol F, are difunctional buildingblocksof several importantpolymers, such as epoxy resins, cyanate esters, benzoxazines, polyesters, polycarboantes, polyeth...
455_ftp
High-Tg Transparent Poly on Phosphinated Bisphe , Introduction Bisphenols, such as bisphenol A or bisphenol F, are difunctional buildingblocksof several importantpolymers, such as epoxy resins, cyanate esters, benzoxazines, polyesters, polycarboantes, polyethers, and poly(ether sulfone)s. Thus, over 106 tons per year of bisphenol A are consumed. As a result, modifications of bisphenols should be of interest to the bisphenol-based industry. Among the bisphenol-based polymers, poly(ether sulfone)s are impor- tant high-performance engineering thermoplastic and well-known for their excellent mechanical, thermal, and gas transport properties.[1–9] They are typically prepared by nucleophilic displacement polymerization of bisphenols with 4, 4’-dihaloaromatic sulfones, where the electronega- tive sulfone group activates the halides to nucleophilic displacement. Poly(ether sulfone)s are naturally transpar- applications in some electronic field. In contrast, polyimides, although exhibit high Tg, are typically yellow to amber in color. The intermolecular charge-transfer complex (CTC) formation is responsible for the color of polyimides. The intermolecular CTC is derived fromthe interactionbetweenelectron-donor (diamine) and electron-acceptor (dianhydride) groups, so the CTC forma- tion can be reduced by incorporating an electron-donating group into a dianhydride or introducing an electron- withdrawing group into a diamine.[10] The intermolecular CTC formation can also be reduced by introducing a bulky pendent group to prevent the polyimide chains from being well-stacked. Reducing conjugation or introducing alipha- tic dianhydride/diamine is another method to lighten the color of polyimides.[11–14] However, because the aliphatic segments are less stable, the thermal stability of aliphatic polyimides is not high. As to aromatic polyimides, unless diamines[15] or dianhydrides[16] with extremely bulky their applications in flexible display. It has been reported that incorporating asymmetric , Full Paper lym r s d. se f w pendants[17–30] into polymers can enhance the Tg of polymers due to restricted segmental mobility. As a result preparation of bisphenol monomers with bulky pendant for poly(ether sulfone)s may be a route for high-Tg poly(ether sulfone)s. Herein, three poly(ether sulfone)s C. H. Lin, S. L. Chang, T. P. Wei Department of Chemical Engineering, National Chung Hsing University, Taichung, Taiwan E-mail: linch@nchu.edu.tw ent and exhibitmoderate to high Tg. However, compared to polyimides, their Tgs are not high enough, limiting their pendant are employed, polyimideswith cutoff wavelength less than 350nm are rarely seen in the literature, limiting Ching Hsuan Lin,* Sheng Lung Chang The preparation of high-Tg transparent po phosphinate pendants is described. Poly(ethe phinate-substituted bisphenols were prepare studied and compared with a bisphenol-A-ba foldable, and highly transparent with a cutof ively. They display higher glass tran- sition temperature (258 and 274 8C) and lower coefficient of thermal expansion (d¼ 48ppm per 8C by TMA) than those of P0 (208 8C and d¼ 57ppm per 8C). HO Macromol. Chem. Phys. 2011, 212, 455–464 � 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlin (ether sulfone)s Based nols Tsai Pei Wei ers from poly(ether sulfone)s with bulky ulfone)s P1–P3 based on biphenylene phos- The thermal properties of P1 and P2 were d poly(ether sulfone). P1 and P2 are flexible, avelength around 327 and 328nm, respect- P OO pTSA OH O X H Y Y P O C OH O HO X Y Y X=CH3; Y=H for (1) X=CH3; Y=CH3 for (2) X=H; Y=H for (3) H-OH+ elibrary.com DOI: 10.1002/macp.201000505 455 P1–P3 based on three biphenylene phosphinate-substi- tuted bisphenols 1–3 were prepared. The reaction condi- tions for preparing P1–P3 were discussed. The thermal properties of poly(ether sulfone)s were evaluated and compared with those of the bisphenol-A-based poly(ether sulfone) (P0). Experimental Part Materials Synthesis of (3) DOPO (10.81 g, 0.05mol), 4-hydroxybenzaldehyde 6.11 g (0.05mol), p-TSA 0.432 g (4wt.-% relative to DOPO) and phenol 23.2 g (0.25mol) were introduced into a 250-mL round-bottom glass flask equipped with a nitrogen inlet and a magnetic stirrer (Scheme 2). Themixturewas stirred at 130 8C for 24h. After that, excess phenol was removed by a rotary evaporator. The crude product was dissolved in ethanol and poured into hot water to remove residual phenol. 13.9 g (67% yield) 3 (Scheme 1) were obtained as a yellow powder. After recrystallization from DMAc/methanol solution, a 23 1 2 3 4 5 6 78 9 10 11 12 13 14 15 16 1718 19 20 21 22 P OO CH3 HO OH (2) 10 11 14 15 1 2 3 4 5 6 78 12 1817 19 20 21 22 23 P OO CH3 O O S O O 30 2928 2726 2524 n (P1) Scheme 1. Structures of (2), (3), and (P1). pTSA OH O Y P O C OH O HO X Y Y X=CH3; Y=H for (1) X=CH3; Y=CH3 for (2) X=H; Y=H for (3) H-OH+ 456 www.mcp-journal.de C. H. Lin, S. L. Chang, T. P. Wei P OO HO X H Y 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) waspurchased fromTCI. 4-Hydroxyacetophenone, 4-hydroxybenz- aldehyde, 4,4’-difluorodiphenylsulfone (DFS), 4,4’-dichlorodiphe- nyl ulfone (DClS), cesium fluoride, and p-toluenesulfonic acid (p-TSA) were purchased from Arcos. Phenol and potassium carbonate were purchased from Showa. Both N,N-dimethylform- amide (DMAc) and tetrahydrofuran (THF)were distilled over CaH2. The other solvents used are commercial products (HPLC grade) and used without further purification. Bisphenol (1) was prepared according to our previous paper.[31] Synthesis of (2) DOPO (10.81 g, 0.05mol), 4-hydroxyacetophenone6.81 g (0.05mol), p-TSA 0.432 g (4wt.-% relative to DOPO) and 2,6-dimethylphenol 30.54 g (0.25mol) were introduced into a 250-mL round-bottom glass flask equipped with a nitrogen inlet and a magnetic stirrer. The mixture was stirred at 130 8C for 24h. After that, the mixture was poured into toluene to remove excess 2,6-dimethylphenol. 21.8 g (96% yield) 2 (Scheme 1) were obtained as a yellow powder. After recrystallization from acetic acid, a neat and sharp melting point at 281 8C was observed in the DSC scans. C25H19O4P (456.149): HR-MS (FAB þ) m/z¼ 457.1571 (Mþ 1). Calcd. C 73.67, H 5.52, O 14.02; Found C 73.41, H 5.74, O 14.83. 1H NMR (DMSO-d6): d¼ 1.59 (3H, H6), 1.98 (6H, H22), 6.63 (2H, H2), 6.83 (2H, H20), 7.09 (1H, H17), 7.13 (1H, H15), 7.16 (2H, H3), 7.22 (1H, H11), 7.32 (1H, H16), 7.36 (1H, H10), 7.65 (1H, H9), 7.91 (1H, H14), 8.03 (1H, H8), 8.13 (1H, OH), 9.42 (1H, OH). 13C NMR (DMSO-d6): d¼ 16.85 (C22), 24.38 (C6), 51.51 (C5), 114.59 (C2), 118.85 (C17), 120.76 (C12), 121.98 (C7), 123.16 (C8), 123.34 (C21), 123.80 (C15), 125.21 (C14), 127.81 (C10), 128.55 (C20), 130.12 (C16), 130.54 (C3), 131.87 (C11), 132.52 (C13), 133.28 (C9),136.15 (C4), 136.19 (C19), 150.90 (C18), 151.76 (C23), 156.23 (C1). Scheme 2. Synthesis of (1–3). Macromol. Chem. Phys. 2 � 2011 WILEY-VCH Verlag Gmb 1 2 3 4 5 6 78 9 12 13 16 1718 19 20 21 22 (3) P OO H HO OH 9 10 11 13 14 15 16 011, 212, 455–464 H & Co. KGaA, Weinheim www.MaterialsViews.com neat and sharp melting point at 292 8C was observed in the DSC scans. C25H19O4P (414.1021): HR-MS(FABþ ) m/z¼415.1107 (Mþ 1). Calcd. C 72.46, H 4.62, O 15.44; Found C 72.02, H 4.43, O 15.29. 1H NMR (DMSO-d6): d¼ 4.47 (1H, H6), 6.69 (2H, H21), 6.71 (2H, H2), 7.07 (1H, H17), 7.19 (2H, H20), 7.28 (2H, H3), 7.31 (1H, H15), 7.39 (1H, H10), 7.44 (1H, H16), 7.47 (1H, H11), 7.67 (1H, H9), 8.10 (1H, H8), 8.13 (1H, H14), 9.40 (2H, OH). 13C NMR (DMSO-d6): d¼49.08 (C5), 115.19 (C21), 115.35 (C2), 120.02 (C17), 122.12 (C7), 123.95 (C8), 124.80 (C15), 125.85 (C14), 126.07 (C12), 126.97 (C13), 128.07 (C10), 130.29 (C20), 130.74 (C16), 130.89 (C11), 131.11 (C3), 133.39 (C9), 135.09 (C4,19), 148.97 (C18), 156.40 (C1,22). Synthesis of P1 To a 100mL three-neck round-bottom flask equipped with a magnetic stirrer, nitrogen inlet, bisphenol (1) 3.2878g (7.67mmol),K2CO3 2.1213g (15.34mmol), DFS 1.9511g (7.67mmol), and DMAc 21g were added. The mixture was stirred at 130 8C for 12h. After cooling to room temperature, the solution was poured into 300mL methanol. The fiber-like precipitate was filtered and extracted by methanol in a Soxhlet extractor for 12h, and thendried inavacuumovenat 150 8C. Theyield is quantitative. The fiber-likeP1 (Scheme1)wasdissolved inDMAcinaconcentrationof 20wt.-% and cast on glass by an automatic film applicator. The films were dried overnight at 80 8C and dried at 100 (1h) and 200 8C (2h). 1HNMR (DMSO-d6): d¼ 1.72 (3H,H6), 6.90 (2H,H2), 6.92 (1H,H17), 6.93 (1H, H11), 7.02 (2H, H29), 7.04 (2H, H24), 7.09 (2H, H21), 7.13 (1H, H15), 7.30 (2H, H20), 7.32 (1H, H16), 7.39 (2H, H3), 7.41 (1H, H10), 7.68 (1H, H9), 7.94 (2H, H28), 7.96 (2H, H25), 7.98 (1H, H14), 8.10 (1H, H8). P2 and P0were prepared in a similar procedure using (2) and bisphenol A as the starting materials, respectively. Characterization DSC was carried out on a Perkin-Elmer DSC 7 in nitrogen atmosphere at a heating rate of 20 8C �min�1. Thermal gravi- metric analysis (TGA) was performedwith a Seiko EXSTAR 600 at a heating rate of 20 8C �min�1 under nitrogen atmosphere. Dynamic mechanical analysis (DMA) was performed with a Perkin-Elmer Pyris Diamond DMA with a sample size of 5.0� 1.0�0.002 cm3. The storage modulus E0 and tan d were determined as the samplewas subjected to the temperature scan mode at a programmed heating rate of 5 8C �min�1 at a frequency of 1Hz. The test was performed by tension mode with an amplitude of 25mm. Thermal mechanical analysis (TMA) was performed with a Perkin-Elmer Pyris Diamond TMA at a heating rate of 5 8C �min�1. The onset of transition in dimension was defined as Tg, and the coefficient of thermal expansion (CTE) P H OO H+P O X O P OO H tro stit -se High-Tg Transparent Poly(ether sulfone)s . . . www.mcp-journal.de HO O X P O C X O HO HO -H2O nucleophilic addition elec sub (regio P O C X O HO resonance the carbocationis stabilizedby resonance Scheme 3. Proposed mechanism for the synthesis of (1–3). www.MaterialsViews.com Macromol. Chem. Phys. 2 � 2011 WILEY-VCH Verlag Gmb P O X O HO OH OH X OHO H P O C X O HO OH H H2O H3O philic ution lective) (1-3) OH Y Y Y Y Y Y X=CH3; Y=H for (1) X=CH3; Y=CH3 for (2) X=H; Y=H for (3) 011, 212, 455–464 H & Co. KGaA, Weinheim 457 ata from 40 to Tg – ing a Varian Inova was calibrated by 9. Gel permeation tachi L2130 with a mide (DMF) as the �1. The data were ra were measured eter in KBr powder performed by a Finnigan/Thermo Quest MAT 95XL mass spectrometer. shiftduetotheelectron-donatingcharacteristicofdimethyl group. The signals of Ar-H, assigned by the assistance of 1H-1H COSY, confirm the structure of (2). In the 13C NMR spectrum, due to the P-C 1J coupling, the signals of carbon 5 split into two peaks at d¼ 51.51 and 52.12 with a coupling constant of 92.03Hz. Because of the same reason, the signals of carbon 7 split into two peaks at d¼ 121.98 and 122.73with a coupling constant of 113.15Hz. The signals of aromatic carbon, assigned by the assistance of H-13C HETCOR NMR spectrum, also confirm the structure of (2). Figure 2 shows the (a) 1H and (b) 13C NMR spectra of (3), and the peak patterns are consistent with the structure of (3). 458 www.mcp-journal.de C. H. Lin, S. L. Chang, T. P. Wei in preparing 3]. As a result, the electro- philic substitution can carry out easily with high yield. Characterization of (2) and (3) Figure 1 shows the (a) 1H and (b) 13CNMR spectra of (2). In the 1H NMR spectrum, the signals of methyl group were split into two peaks with a coupling constant of 17.4Hzbecauseof a 3JP-H coupling. Two phenol peaks at d¼ 8.2 and 9.4 were observed. The phenol adjacent to 1 Results and Discussion Synthesis of Bisphenols Bisphenols 2 and 3were prepared by the reaction of DOPO, 4-hydroxyacetophe- none (or 4-hydroxybenzaldehyde), and excess 2,6-dimethylphenol (or phenol) usingp-TSAas catalyst (Scheme2). Excess 2,6-dimethylphenol (or phenol) plays the roles of both reactant and reaction medium. Scheme 3 shows the proposed mechanism for the synthesis. DOPO initially attacks the carbonyl group via a nucleophilic addition, forming a ter- tiary (or secondary) hydroxyl group. The hydroxyl group is then protonated by acid. Then, spontaneous dissociation of the protonated hydroxyl group occurs to yield a carbocation intermediate plus water. Finally, 2,6-dimethyl phenol (or phenol) reacts with the resulting carbo- cation via an electrophilic substitution, yielding 2 or 3, respectively. In this mechanism, the carbocation can be stabilized by the electron-donating phe- nolic OH, making the carbocation stable [even the carbocation is a secondary one before Tg was defined by calculating the TMAd 20 8C. NMRmeasurements were performed us 600NMR in DMSO-d6, and the chemical shift setting the chemical shift of DMSO-d6 as d¼ 2.4 chromatography (GPC) was carried out on a Hi UV detector (L2400) using N,N-dimethylforma eluent at 60 8C with a flow rate of 1.0mL �min calibrated with polystyrene standard. IR Spect by a Perkin-Elmer RX1 infrared spectrophotom form. High resolution mass spectra were dimethyl groups has smaller chemical Figure 1. (a) H NMR Macromol. Chem. Phys. 2 � 2011 WILEY-VCH Verlag Gmb 13 and (b) C NMR spectra of (2) (in DMSO-d6). 011, 212, 455–464 H & Co. KGaA, Weinheim www.MaterialsViews.com This result is speculated with the config- uration of the carbocation intermediate in the electrophilic substitution. Gener- ally, the configuration of carbocation intermediate is not planar, so the electro- philic substitutionwill occurnon-equally from the both faces. One of the two faces is likely, for steric reasons, tobeabitmore accessible than the other face, leading to diastereomers with unequal amounts of RR and RS ratio. Scheme 4 shows the proposed mechanism for the regioselec- tive electrophilic substitution. According to the minimum energy model of carbo- cation (calculated by ChemBio 3D Ultra High-Tg Transparent Poly(ether sulfone)s . . . www.mcp-journal.de As shown in Scheme 2, bisphenol (2) is an asymmetric bisphenol. Generally, the bisphenols[32–36] could be pre- pared by acid-catalyzed condensation of ketone or alde- hyde-containing compoundswith excess phenol. However, only symmetric bisphenols can be obtained by that approach. However, asymmetric bisphenols can easily be preparedby this strategybychoosing substitutedphenol as reactants. Since the phosphorus and aliphatic carbon in bisphenol (2) are both chiral centers, four stereoisomers should be resulted. Theoretically, each stereocenter can be either R or S configuration, and hence, the possible combinations are RR, RS, SR, and SS configurations. The four stereoisomers can be grouped into two pairs of enantiomers, resulting in two diastereomers: RRþ SS and RSþRS. The RR stereoisomer is the enantiomer of the SS stereoisomer, and is diastereomerically related to the RS and SR stereoisomers. However, according to the NMR spectra of (2), only one pair of the diastereomers, not two pairs of diastereomers, was obtained in this synthesis. That means that this reaction is a 100% regioselective reaction. A, (1–2) with DFS in DMAc (or DMAc/ results are listed i weight for P0–P2 respectively. Figu spectra of P1. The Figure 2. (a)1H NMR and (b)13C NMR spectra of (3) (in DMSO-d6). Scheme 4. Propo philic substitutio www.MaterialsViews.com Macromol. Chem. Phys. 2011, 212, 455–464 � 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhe Toluene) using potassium carbonate as catalyst (Scheme5andTable1, Runs1–2). The molecular weight of P0–P2 was measured by means of GPC, and the n Table 2. The number-averagemolecular is 1.00� 105, 1.02� 105, and 1.24� 105, re 3 shows the (a)1H and (b)13C NMR assignment of each peak, assisted by the sed mechanism for the regioselective electro- on the right face. This explains theperfect regioselectivity. However, detailed experiment is still required to confirm this speculation. Synthesis and Characteristics of Poly(ether sulfone)s P0–P2 were successfully prepared by nucleophilic substitution of bisphenol 11.0), the left face is severely blocked by the biphenylene and the phenol groups, so electrophilic substitution of 2,6- dimethyl phenol occurs exclusively only n. im 459 K 460 www.mcp-journal.de C. H. Lin, S. L. Chang, T. P. Wei S O O FF+ P O C O HO OH X Y Y 1H-1H COSY and 1H-13C HETERCOSY spectra, supports the structure of P1. Figure 4 shows the 1HNMR spectrum of P2. One can see the characteristic dimethyl peak (H22) at d¼ 1.6, and the assignment of other peaks supports the structure of P2. Generally, fluorine end groups have a higher reactivity than chloride end groups toward the nucleophilic substitu- tion, butDFS ismuchexpensive than theDClS. To reduce the cost, DClS was applied to replace DFS to prepare P1 (Run 3). However, after reacting at 130 8C for 12h, a small Scheme 5. Synthesis of P1–P3. Table 1. Polymerization conditions for P1. Run Reactant Temperature -C 1 DFS 130 2 DFS 130 3 DClS 130 4 DClS 130 5 DClS 120 6 DClS 130 7 DClS 145 8 DClS 160 Table 2. GPC data and thermal properties of P0–P2. Sample Mn a) Mw b) E(c) tan d c) Tg (DSC) 105 105 GPa -C -C P0 1.00 1.75 3.9 208 194 P1 1.02 1.85 5.5 258 240 P2 1.24 2.05 4.9 274 253 a)Number-average molecular weight (relative to polystyrene standar c)Measured by means of DMA at a heating rate of 5 8C �min�1, storage at a heating rate of 20 8C �min�1; e)Measured by TMA at a heating rat from 50 8C to Tg – 20 8C; g)Temperature corresponding to 5wt.-% loss b atmosphere; h)At 800 8C in nitrogen atmosphere. Macromol. Chem. Phys. 2 � 2011 WILEY-VCH Verlag Gmb 2CO3 P O C O O O X S O O n Y Y X=CH3, Y=H for P1 X=CH3; Y=CH3 for P2 X=H; Y=H for P3 ph-CH(CH3)-ph signal at d¼ 5.5 was observed in the 1H NMR spectrum (Figure 5). In addition to the CH signal, the signals of Ar-H were reduced apparently. Obviously, a cleavage of the P–C bond occurred during the preparation. At thismoment, it is speculated that the lower reactivity of chloride end groups increase the life time of phenolate, which will attack the electron deficient phosphorus atom, resulting in a cleavage of P–C bond. However, such a speculation still needs investigation. The cleavage Solvent Result DMAc successful DMAc/toluene successful DMAc P–C cleavage DMAc/toluene P–C cleavage DMAc incomplete NMP incomplete NMP P–C cleavage NMP P–C cleavage d) Tg (TMA)e) CTEf) Td,5%g) Char yieldh) -C 10�6 -C�1 -C wt.-% 202 57 506 41 240 48 451 43 262 48 456 40 d, using DMF as the eluent); b)Weight-average molecular weight; modulus (E0) recorded at 50 8C; d)From the second DSC heating scan e of 10 8C �min�1; f)Coefficients of thermal expansion are recorded y thermogravimetry at a heating rate of 20 8C �min�1 in nitrogen 011, 212, 455–464 H & Co. KGaA, Weinheim www.MaterialsViews.com High-Tg Transparent Poly(ether sulfone)s . . . www.mcp-journal.de phenomenonwasalsoobservedusingDMAc/tolueneas the solvent (Run 4), in which water was distilled during the reaction. When the reaction was reduced to 120 8C to avoid the cleavage (Run 5), some residual peaks of (1) were observed, indicating that the reaction was not complete at the lower reaction temperature. In addition, the prepara- tionwasnot successfulwhenthesolventwaschanged from DMAc toN-methylpyrrolidone (NMP) (Runs 6–8). Thus, it is not easy to prepare P1 using DClS as reactant. Various attempts have been made to prepare P3 by nucleophilic substitutionof (3)andDFSusingK2CO3orcesiumfluorideas catalyst. However, after reaction, the signal of methine [(O¼ P)C–H] of (3) at d¼ 5.0 disappears, while a sign
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