Bis allyl benzoxazine: Synthesis, polymerisation and polymer properties

A bis benzoxazine monomer with allyl groups viz: 2,2′-bis (8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) was synthesized via a solventless method from 2,2′diallyl bisphenol-A, paraformaldehyde and aniline. The chemical structure of Bz-allyl was confirmed by FTIR, ¹H NMR and ¹³C NMR analyses. The monomer manifested a two-stage thermal polymerisation pattern. The first stage was attributed to the polymerisation of the allyl groups and the second to the ring - opening polymerisation of benzoxazine moiety. The polymerisation profile was investigated with DSC, FT-IR, TGA and pyrolysis-GC techniques. A polymerisation mechanism involving the electrophilic addition of the propagating iminium cation on the aniline ring in lieu of the activated sites of bisphenol-A, (which are blocked by allyl and alkyl substituents) was proposed. Additional cross-linking was provided by thermal addition polymerization of allyl groups. As a result of altered cross-linking via the aniline moiety and the additional cross-linking via allyl groups, the cured polymer exhibited a T_g of ca. 300 °C and high crosslink density. The thermal stability of this polymer was also substantially higher vis-à-vis that of the bisphenol-A based polybenzoxazine. The work focuses on the manipulation of benzoxazine monomer structure to alter the ring-opening polymerisation mechanism and cross-linking to derive polybenzoxazine with improved properties.     

Benzoxazine-bismaleimide blends: Curing and thermal properties

A blend of bisphenol A based benzoxazine (Bz-A) and a bismaleimide (2,2-bis[4(4-maleimidophenoxy) phenyl] propane (BMI), was thermally polymerised in varying proportions and their cure and thermal characteristics were investigated. The differential scanning calorimetric analysis, supplemented by rheology confirmed a lowering of the cure temperature of BMI in the blend implying catalysis of the maleimide polymerisation by benzoxazine. FTIR studies provided evidences for the H-bonding between carbonyl group of BMI and -OH group of polybenzoxazine in the cured matrix. The cured matrix manifested a dual phase behaviour in SEM and DMTA with the minor phase constituted by polybenzoxazine dispersed in an interpenetrating polymer network (IPN) of polybenzoxazine and cured BMI. The IPN possessed improved thermal stability over the constituent polybenzoxazine. A benzoxazine monomer possessing allyl functional groups, 2,2′-bis(8-allyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Bz-allyl) was reactively blended with the same bismaleimide in varying stoichiometric ratios (Bz-allyl/BMI), where the curing involved mainly Alder-ene reaction between allyl- and maleimides groups and ring-opening polymerisation of benzoxazine. The rheological analysis showed the absence of catalytic polymerisation of BMI in this case. The overall processing temperature was lowered in the blend owing to the co-reaction of the two systems to form a single-phase matrix. The cured resins of both Bz-A/BMI and Bz-allyl/BMI blends exhibited better thermal stability than the respective polybenzoxazines. The T_g of the IPN was significantly improved over that of polybenzoxazine (Bz-A). However, the co-reaction resulted in a marginal decrease in the T_g of the system in comparison to the polybenzoxazine (Bz-allyl).     

Development of polybenzoxazine–silica–titania (PBZ–SiO2–TiO2) hybrid nanomaterials with high surface free energy

In the present work, silica and titania reinforced polybenzoxazine (PBZ–SiO₂–TiO₂) hybrid nanomaterial possessing high surface free energy have been developed using dimethylol-functional benzoxazine monomer (4HBA-BZ), tetraethoxysilane (TEOS), 3-(isocyanatopropyl)triethoxysilane (ICPTS), titaniumisopropoxide (TIPO) through an in situ sol–gel process. Data obtained from the contact angle measurement indicate that the hybrid materials are hydrophilic in nature and possess a high surface free energy. For example, hybrid PBZ obtained from 1:1:0.6:0.4 (m:m:w:w) ratio of 4HBA-BZ:ICPTS:TEOS:TIPO (PBST₄) exhibit a high surface free energy of 38.2 mJm^?2 which is higher than that of neat polybenzoxazine (29.5 mJm^?2). Further data resulted from thermal studies indicate that the hybrid PBZ possess higher values of T_g, thermal stability and char yield than those of neat PBZ.     

Synthesis and characterization of polybenzoxazine containing phosphorus

The novel benzoxazine monomer containing phosphorus has been synthesized based on multifunctional amine route from bis(4-aminophenyl)phenylphosphate,p-cresol and formaldehyde.Subsequently,the benzoxazine monomer was thermo-cured into polybenzoxazine containing phosphorus.The chemical structures were identified by nuclear magnetic resonance(NMR),Fourier transform infrared spectroscopy(FT-IR).The curing reaction was monitored by differential scanning calorimetry(DSC) and FT-IR.The thermal and flame-retardant properties of obtained polybenzoxazine were evaluated by dynamic mechanical thermal analysis(DMA),thermal gravimetric analysis(TGA) and oxygen index meter, respectively.The results show that the novel polybenzoxazine has high limiting oxygen index(38.1) and glass transition temperature(232℃).     

Thermal degradation characteristics of polysulfones with benzoxazine end groups

Thermal degradation behaviors of phenol and benzoxazine end-capped polysulfone macromonomers (PSU-OH and PSU-P-a) and pre-cured PSU-P-a in the absence and presence of aniline and phenol based benzoxazine monomer (P-a) were investigated via pyrolysis mass spectrometry. A significant increase in thermal stability of both polysulfone and polybenzoxazine chains upon polymerization of benzoxazine end groups was determined compared to phenol-ended polysulfones and aniline based monofunctional polybenzoxazine. Thermal stability of both chain segments depends on concentration of benzoxazine monomer and the chain length of the polysulfone chain.     

Surface Properties and Hydrogen Bonds of Mono-functional Polybenzoxazines with Different N-substituents

A series of mono-functional benzoxazine monomers with different N-substituents were synthesized from phenol, formaldehyde, and various amines(ammonia, methylamine, n-butylamine, dodecylamine), named P-am, P-m, P-b, and P-da, respectively. The surface properties of these polybenzoxazine films were proven by contact angle measurements. The hydrogen bond network of the polybenzoxazine systems was studied using the FTIR spectra. And the results showed that the surface free energy increased with increasing the fraction of intermolecular hydrogen bonding when the N-substituent was an alkyl chain. However, the rule was not suitable when the N-substituent was H. That was because there was one more kind of intramolecular hydrogen bond in the poly(P-am). Based on these findings, we proposed that both the N-substituent alkyl group and the fraction of intermolecular hydrogen bonding had effects on the surface free energy.     

Optical,electrochemical, and thermal behavior of polybenzoxazine copolymers incorporated with tetraphenylimidazole and diphenylquinoline

Two new polybenzoxazine copolymers were synthesized by polymerizing conventional benzoxazine monomer with varying weight percentage of tetraphenylimidazole and diphenylquinoline. The tetrasubstituted imidazole was synthesized through Debus‐Radziszewski imidazole synthesis method, and quinoline derivative was synthesized through Friedlander quinoline synthesis, and their structure was confirmed through FTIR, ¹HNMR, and MASS spectral analysis. New polybenzoxazine copolymers were synthesized by polymerizing conventional benzoxazine monomer with varying weight percentage of (10, 20, and 30%) of phenolic tetraphenylimidazole and diphenylquinoline. The polybenzoxazines cocured with 10, 20, and 30 wt% of imidazole derivative showed a band gap of 2.27, 2.08, and 2.2 eV, respectively, and the quinoline derivative incorporated at 10, 20, and 30 wt% in to polybenzoxazines exhibited a band gap of 2.26, 2.3, and 2.03 eV, respectively. The polybenzoxazines cocured with phenolic imidazoles and quinolines have high glass transition and thermal degradation stability in addition to significant improvement in optical and electrochemical properties than that of conventional bisphenol‐based polybenzoxazines.     

Synthesis and properties of new polybenzoxazines containing (substituted) cyclohexyl moieties

A series of new polybenzoxazines were synthesized based on diphenols containing (substituted) cyclohexyl moiety and were characterized by FT‐IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. These new benzoxazine monomers exhibited better processability with lower peak cure temperature and a wide cure controllable window (CCW) as manifested in differential scanning calorimetric analysis. The cure analysis was performed by FT‐IR spectroscopy. Glass transition temperature of new polybenzoxazines varied from 170 to 205°C. The cyclohexyl bridge groups facilitated ring opening, resulting in polymer with improved thermal stability in comparison to bisphenol A‐based benzoxazine as assessed by the various thermal analyses. The water contact angles of polybenzoxazines containing (substituted) cyclohexyl moieties were higher than that of bisphenol A‐based polybenzoxazine, implying their higher hydrophobicity. Copyright © 2009 John Wiley & Sons, Ltd.     

Surface properties and hydrogen bonds of mono-functional polybenzoxazines with different <Emphasis Type="Italic">N</Emphasis>-substituents

A series of mono-functional benzoxazine monomers with different N-substituents were synthesized from phenol, formaldehyde, and various amines (ammonia, methylamine, n-butylamine, dodecylamine), named P-am, P-m, P-b, and P-da, respectively. The surface properties of these polybenzoxazine films were proven by contact angle measurements. The hydrogen bond network of the polybenzoxazine systems was studied using the FTIR spectra. And the results showed that the surface free energy increased with increasing the fraction of intermolecular hydrogen bonding when the N-substituent was an alkyl chain. However, the rule was not suitable when the N-substituent was H. That was because there was one more kind of intramolecular hydrogen bond in the poly(P-am). Based on these findings, we proposed that both the N-substituent alkyl group and the fraction of intermolecular hydrogen bonding had effects on the surface free energy.     

Synthesis, curing kinetics and thermal properties of bisphenol-AP-based benzoxazine

A novel bisphenol-AP-aniline-based benzoxazine monomer (B-AP-a) was synthesized from the reaction of 4,4′-(1-phenylethylidene) bisphenol (bisphenol-AP) with formaldehyde and aniline. The chemical structures were identified by FT-IR, ¹H and ¹³C NMR analyses. The polymerization behavior of the monomer and the types of hydrogen bonding species were monitored by differential scanning calorimetry (DSC) and FT-IR. The curing kinetics was studied by isothermal DSC and the isothermal kinetic parameters were determined. The thermal properties of cured benzoxazine were measured by DSC and thermogravimetric analysis (TGA). The bisphenol-AP-aniline-based polybenzoxazine (poly(B-AP-a)) exhibited higher glass transition temperature (T_g) and better thermal stability than corresponding bisphenol A-aniline-based polybenzoxazines (poly(BA-a)). The T_g value of poly(B-AP-a) is 171 °C. The temperatures corresponding to 5% and 10% weight loss is 317 and 347 °C, respectively, and the char yield is 42.2% at 800 °C. The isothermal curing behavior of B-AP-a displayed autocatalysis and diffusion control characteristics. The modified autocatalytic model showed good agreement with experimental results.     

Cyclohexane and phosphorus based benzoxazine-bismaleimide hybrid polymer matrices: thermal and morphological properties

Benzoxazine monomers namely 1,1-bis (3-methyl-4-hydroxyphenyl)cyclohexane benzoxazine (CB_DDM) and bis(4-maleimidophenyl) triphenylphosphine oxide benzoxazine (BMPB_BAPPPO) were synthesized and blended with bismaleimide (BMPM) to improve thermal properties of polybenzoxazine. The benzoxazine- bismaleimide (Bz-BMI) hybrid polymer matrices were prepared via in-situ polymerization and their thermal and morphological properties were studied. The chemical reaction of benzoxazines with the bismaleimide was carried out thermally and the resulting product was analyzed by FT-IR spectra. The glass transition temperature, curing behavior, thermal stability, char yield and flame resistance of the hybrid polymer matrices were analyzed using DSC and TGA. The homogeneous structure of the hybrid polymer matrices was determined by SEM and visual observations. Data obtained from thermal studies infer that these hybrid materials possess high thermal stability which can be used as adhesives, sealants, coating and matrices for high performance automobile and microelectronic applications.     

Synthesis of novel tri‐benzoxazine and effect of phenolic nucleophiles on its ring‐opening polymerization

A trifunctional benzoxazine, 1,3,5‐tris(3‐phenyl‐3,4‐dihydro‐2H‐benzo[1,3]oxazin‐6‐yl)benzene (T‐Bz) was synthesized and in an effort to reduce its curing temperature (curing maxima at 238 °C), it was mixed with various phenolic nucleophiles such as phenol (PH), p‐methoxy phenol (MPH), 2‐methyl resorcinol (MR), hydroquinone (HQ), pyrogallol (PG), 2‐naphthol (NPH), 2,7‐dihydroxy naphthalene (DHN), and 1,1'‐bi‐2‐naphthol (BINOL). The influence of these phenolic nucleophiles on ring‐opening polymerization temperature of T‐Bz was examined by DSC and FTIR analysis. T‐Bz undergoes a complete ring‐opening addition reaction in the presence of bi‐ and trifunctional phenolic nucleophiles (MR/HQ/PG/DHN) at 140 °C (heated for 3 h) and forms a networked polybenzoxazine (NPBz). The NPBzs showed a high thermal stability with T_d20 of 350–465 °C and char yield of 67–78% at 500 °C; however, a diminutive weight loss (6.9–9.8%) was observed at 150–250 °C (T_d5: 215–235 °C) due to degradation of phenolic end groups. This article also gives an insight on how the traces of phenolic impurities can alter the thermal properties of pure benzoxazine monomer as well as its corresponding polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2811–2819     

Study of hydrogen bonding and thermal properties of polybenzoxazine and poly‐(ε‐caprolactone) blends

The thermal properties of physical blends containing benzoxazine monomer and polycaprolactone (PCL) were monitored by DSC and Fourier transform infrared spectroscopy (FTIR). The ring‐opening reaction and subsequent polymerization reaction of the benzoxazine were facilitated significantly by the presence of a PCL modifier. Hydrogen‐bond formation between the hydroxyl groups of polybenzoxazine and the carbonyl groups of PCL was evident from the FTIR spectra. Only one glass‐transition temperture (T_g) value was found in the composition range investigated, and the T_g value of the resulting blend appeared to be higher in the blend with a greater amount of PCL. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 736–749, 2001     

Studies on the mesophase formation mechanism of polybenzoxazines: polymerisation induction

ABSTRACT

To study the mesophase formation mechanism of polybenzoxazine, a novel linear benzoxazine oligomer bearing cholesteryl side groups [poly(PC-AC)] was designed and synthesised through thermally activated ring-opening polymerisation of a monofunctional benzoxazine monomer (PC-AC). The PC-AC was obtained by Mannich condensation reaction using mesomorphic amine of cholesteryl 4-aminobenzoate, p-cresol and paraformaldehyde as starting materials. During the isothermal polymerisation of PC-AC monomer, the phase evolution from a crystal phase to an isotropic molten phase and then to a liquid crystal (LC) phase was observed. Since it is PC-AC oligomers that form the LC phase, ‘polymerisation-induced LC’ mechanism is put forward. We believe that the structure factors including the confined formation of intramolecular hydrogen bonding and the side chain position of mesogenic units also play an important role in the formation of the LC phase. Furthermore, poly(PC-AC) exhibits a smectic mesophase. This work provides new insight into the LC phase formation mechanism of polybenzoxazines. This is very helpful to guide the rational design and synthesis of polymers with high thermal conductivity and high-temperature resistance.     

Synthesis of polybenzoxazine/clay nanocomposites by in situ thermal ring‐opening polymerization using intercalated monomer

A new class of polybenzoxazine/montmorillonite (PBz/MMT) nanocomposites has been prepared by the in situ polymerization of the typical fluid benzoxazine monomer, 3‐pentyl‐5‐ol‐3,4‐dihydro‐1,3‐benzoxazine, with intercalated benzoxazine MMT clay. A pyridine‐substituted benzoxazine was first synthesized and quaternized by 11‐bromo‐1‐undecanol and then used for ion exchange reaction with sodium ions in MMT to obtain intercalated benzoxazine clay. Finally, this organomodified clay was dispersed in the fluid benzoxazine monomers at different loading degrees to conduct the in situ thermal ring‐opening polymerization. Polymerization through the interlayer galleries of the clay led to the PBz/MMT nanocomposite formation. The morphologies of the nanocomposites were investigated by both X‐ray diffraction and transmission electron microscopic techniques, which suggested the partially exfoliated/intercalated structures in the PBz matrix. Results of thermogravimetric analysis confirmed that the thermal stability and char yield of PBz nanocomposites increased with the increase of clay content. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Novel functional copolymers based on glycidyl methacrylate: Synthesis,characterization, and polymerization kinetics

A new methacrylate monomer 2-(4-nitrophenyl)-2-oxoethyl-2-methacrylate (NFM) was synthesized and its radical copolymerization with glycidyl methacrylate (GMA) was studied in 1,4-dioxane solution at 65°C using 2,2′-azobisisobutyronitrile as an initiator. The synthesized monomer and copolymers were characterized by FTIR, ¹H and ¹³C-NMR spectroscopy. The analysis of reactivity ratios revealed that NFM is less reactive than GMA, and copolymers formed are statistically in nature. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increasing in the mole fraction of NFM in the copolymers. Glass transition temperatures of the copolymers decreased with an increasing of NFM molar fraction in copolymers. In addition, according to the results obtained from the contact angle and zeta potential measurements the hydrophobic character of the polymer decreases (it means surface free energy increases) and its zeta potential becomes more negative with increase of NFM ratio in the copolymer. Polymers with carbonyl functional groups have been particularly interesting because of their use as photoresists.     

Effect of an Organically Modified Nanoclay on Low‐Surface‐Energy Materials of Polybenzoxazine

Novel low surface free energy materials of polybenzoxazine/organically modified silicate nanocomposites have been prepared and characterized. The CPC (cetylpyridinium chloride)/clay10%/poly(3‐phenyl‐3,4‐dihydro‐2H‐1,3‐benzoxazine) (PP‐a) material possesses an extremely low surface free energy (12.7 mJ · m⁻²) after 4 h curing at 200 °C, which is even lower than that of poly(tetrafluoroethylene) (22.0 mJ · m⁻²) calculated on the basis of the three‐liquid geometric method. X‐Ray photoelectron spectroscopy (XPS) shows a higher silicon content on the surface of the nanocomposites than for an average composition, which implies that the clay is more preferentially enriched on the outermost layer. In addition, the glass transition temperature (T_g) of the polybenzoxazine (PP‐a) in the nanocomposite is 22.6 °C higher and its thermal decomposition temperature is also 31.5 °C higher than the pure PP‐a. This finding provides a simple way to prepare low surface energy and high thermal stability materials.

     

紫外光引发LDPE膜接枝含氟丙烯酸酯的研究

通过紫外光引发表面接枝聚合反应的方法 ,把含氟丙烯酸酯单体R 5 6 1 0引到LDPE薄膜上 .对经丁酮抽提后的接枝膜进行FTIR、ESCA、SEM和DSC等表征 ,证实含氟聚合物以化学键的方式接枝在LDPE基体膜上 .在一定范围内 ,增加紫外光强、引发剂和单体浓度以及反应温度等均有利于提高接枝率 .经计算R 5 6 1 0的紫外光引发接枝聚合反应总活化能为 5 4 2kJ mol.接枝膜的接触角随着接枝率的提高逐步增大 ,直至趋于恒定 .作者提出接枝膜存在一个在接触角测定时影响基体膜与探测水滴相互作用过程的边界层 .当接枝率较低、接枝层厚度小于边界层临界厚度时 ,基体LDPE影响接触角的大小 ,但随着接枝率提高 ,接枝层逐渐变厚 ,氟聚合物层对接触角的贡献逐渐占优势 ,导致接触角随之增大 .当接枝率超过一定值以后 ,接枝层厚度超过边界层临界厚度 ,接枝层对接枝膜的接触角起全部贡献 ,接触角测定值随之稳定     

Preparation and thermal properties of graphene oxide/main chain benzoxazine polymer

Graphene oxide/polybenzoxazine nanocomposites are prepared using main chain benzoxazine polymer (MCBP) via a solvent casting method from different organic solvents. The addition of graphene oxide to the polymeric matrix leads to a gradual decrease in the glass transition temperature of the polymeric matrix. This drop is attributed to the reactive nature of graphene oxide, which undergoes exothermic thermal de-oxygenation before the onset of polybenzoxazine ring opening polymerization upon curing of the nanocomposites. Additionally, it is reported that the glass transition of polybenzoxazine films cast from different solvents depends on the nature of the solvent.     

High performance thermosets from a curable Diels–Alder polymer possessing benzoxazine groups in the main chain

A high‐molecular‐weight polymer (PBz) possessing reactive benzoxazine groups in the main chain was prepared through the Diels–Alder reaction using bis(3‐furfuryl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl)isopropane (BPA‐FBz) and bismaleimide (BMI) as monomers. The chemical structure of PBz is characterized with FTIR and ¹H NMR. The polymer PBz was further thermally reacted with a high performance polymer (PBz‐R) through the ring‐opening addition reaction of benzoxazine groups and the addition reaction of maleimide groups. PBz‐R exhibit a high glass transition temperature of 242 °C, good thermal stability, high flame retardancy, high mechanical strength, and great flexibility. Another crosslinked polymer (PBz‐BR) curing from the mixture of BPA‐FBz and BMI was also prepared. The properties of PBz‐BR are also attractive but, however, not as good as what observed with PBz‐R. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6509–6517, 2008