Advanced chemically induced phase separation in thermosets: Polybenzoxazines toughened with multifunctional thermoplastic main-chain benzoxazine prepolymers

Multifunctional thermoplastic main-chain benzoxazine prepolymers were synthesized and systematically varied in their structure in order to function as high-performance toughener additives. Their unique chemical composition allows multiple covalent crosslinking with many thermoset network systems including benzoxazines and epoxides in conjunction with a defined chemical induced phase separation (CIPS) upon curing. This was successfully shown using a benzoxazine-based thermoset resin matrix as an example. The corresponding morphologies were addressable in a predictable manner and brought into context with the obtained macroscopic mechanical and thermal properties. In this relationship the CIPS process was classified and compared with the literature in more general means for advanced morphology control by differentiating between covalently attached and so-called gradient domain structures. The prepolymers were characterized by ¹H NMR, FT-IR, DSC and TGA. The thermoset morphologies were investigated by TEM and AFM. The fracture toughness (K_Ic) and the elastic modulus (E) were measured by fracture and three point bending experiments. Thermal properties of the resulting films have been tested by DMA.     

Thermally curable benzoxazine-modified vegetable oil as a coating material

In this article, a new synthetic approach for the modification of partial glycerides (PG) obtained from sunflower oil with thermally curable benzoxazine units and its potential use as a coating material are described. For this purpose, hydroxyl-containing benzoxazine monomer was first prepared by conventional ring-forming reaction of phenol with paraformaldehyde in the presence of 6-amino-1-hexanol. The subsequent urethane reaction between PG and the benzoxazine monomer using toluene diisocyanate yields corresponding modified oil. The structures of the intermediates, and the modified triglycerides are confirmed by FTIR and ¹H NMR spectral analysis. Thermally activated curing behaviors of the precursor and the modified oil in the absence of any catalyst were studied by differential scanning calorimetry. Thermal and film properties of the cured products were also investigated.     

Synthesis and characterization of thermally curable polyacetylenes by polymerization of propargyl benzoxazine using rhodium catalyst

A novel acetylene monomer containing benzoxazine group was synthesized and polymerized with [(norbornadiene)rhodium(I) chloride]₂ ([(nbd)RhCl]₂) to give the corresponding polymer. The effect of triethylamine as co-catalyst in the polymerization was investigated. The spectral and thermal analyses confirmed the presence of benzoxazine functionality in the resulting polymer. It is shown that polyacetylene containing benzoxazine side groups undergoes irreversible cis–trans isomerization and thermally activated curing in the absence of any catalyst forming polyacetylene thermoset with high thermal stability.     

A novel benzoxazine monomer with methacrylate functionality and its thermally curable (co)polymers

Benzoxazine monomer with methacrylate functionality, namely 2-(2-(2H-benzo[e][1,3]oxazin-3(4H)-yl)ethoxy) ethyl methacrylate (BEM) was synthesized by simple esterification reaction of hydroxyl containing benzoxazine (B–OH) with methacryloyl chloride, and characterized. BEM was then copolymerized with styrene in 1:4 mol ratio by free radical polymerization using 2,2′-azobis(isobutyronitrile) (AIBN) as initiator. The structure, chemical composition, and molecular weight characteristics of the resulting copolymer were confirmed by FT-IR, ¹H-NMR spectroscopy, and GPC, respectively. The curing behavior and thermal properties of both monomer and copolymer were also studied by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).     

Hyperbranched aliphatic polyester grafted attapulgite via a melt polycondensation process

A new process for the facile fabrication of the hyperbranched polymer grafted nano-surfaces was developed in the present work. The AB₂ type monomer, 2, 2-bis(hydroxymethyl)propionic acid (bis-MPA), was successfully grafted from the surfaces of the amino groups modified attapulgite nano-fibrillar clay (amino-ATP) via a melt polycondensation method with p-toluenesulfonic acid (p-TSA) as catalyst. Higher percentage of grafting (PG%) was achieved within shorter polymerizing time, compared with the product from the solution polycondensation method within longer polymerizing time. The surface composition and crystal structure of the hyperbranched aliphatic polyester grafted attapulgite (HAPE-ATP) were also characterized by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The transmission electron microscopy (TEM) analysis results showed that the dispersibility of the nano-fibrillar clay in organic solvent was improved after the graft polymerization.     

Fabrication and characterisation of cellular alumina articles produced via radiation curable dispersions

A general and versatile method for the production of cellular materials from radiation curable solvent-free colloidal ceramic dispersions containing pore formers has been developed. By this technique cellular ceramic articles with a precisely controlled porosity, cell size and shape are obtained for compositions containing solid pore formers. Monolithic bulk samples are obtained by thermal curing, whereas thin films and multi-layered articles are advantageously produced by UV curing. In this work the influence of three different spherical pore former types, PE, PS and PMMA, on the processing and final properties of the porous materials using alumina as model material is studied. The effect of pore former type and concentration on rheology, curing behaviour, debinding and sintering steps as well as thermal conductivity and mechanical strength of the sintered cellular materials is presented. It is also shown that the choice of pore former type modifies the sintering behaviour and resulting properties.     

Thermally curable aqueous acrylic resins – a new class of duroplastic binders for wood and natural fibers

A new, thermally curable, aqueous acrylic resin is introduced as duroplastic binder for automotive trim parts. This one-component resin has good storage stability and crosslinks upon heating to 180–220°C. Wood fibers are impregnated with the resin using the blow-line technique and can be further processed to fiber mats. With other natural fibers like flax, hemp or sisal, preformed mats are impregnated with the acrylic resin solution. Both methods give prebound fiber mats with good storage stability and thermoplastic deformability. During a final hot press step, the desired shapes are formed and the resin is crosslinked. Composite parts bound with the new acrylic resin show high stiffness and strength and meet the ecological requirements of the automotive industry.     

熔融聚合法直接合成生物降解材料PGLA50/50

以等摩尔乙醇酸、L-乳酸为原料 ,通过熔融聚合法直接合成生物降解材料聚乙醇酸 -乳酸 (PGLA50 / 50 )。当在 1 65℃、70Pa下熔融聚合 1 0h ,以质量分数为 0 .5 %的氯化亚锡为催化剂时 ,产物特性黏数最高可达 0 .1 993dL/g。     

聚L-乳酸固相缩聚工艺研究

以L-乳酸为原料,采用复合催化剂熔融缩聚的方法,制备预聚物,然后进行固相缩聚研究。研究了抽真空和通氮气2种固相缩聚工艺方法。在通氮气工艺方法中探讨了反应温度、反应时间、物料颗粒的尺寸等对固相缩聚反应的黏均相对分子质量的影响。根据缩聚反应平衡和水分子扩散传质平衡的原理对实验现象进行了合理的解释。     

Microwave-assisted synthesis of tetrasubstituted aryl imidazole based polymers via cascade polycondensation process

Poly(Tetrasubstituted Aryl Imidazole)s (PTAIs), a new class of poly(heteroaromatic) polymers was prepared via a cascade polycondensation process, under microwave irradiation. These polymers were obtained by the tetrasubstituted aryl imidazole ring formation involving bis(aryl α-diketone)s, bis(arylaldehyde)s, mono(arylamine)s and ammonium acetate. The polymerization performed under microwave irradiation allowed to get high molecular weight PTAIs in very short reaction times. The chemical structure of these PTAIs was confirmed by NMR spectroscopy. Thermogravimetric analyses (TGA) showed a very good grade of thermal stability of these polymers. Glass transition temperatures (T_g) of PTAIs ranging from 155 °C to 265 °C were determined by Differential Scanning Calorimetry (DSC).     

Preparation and characterization of novel main-chain azobenzene polymers via step-growth polymerization based on click chemistry

A novel α-azide and ω-alkyne A–B type azobenzene monomer, 3′-ethynylphenyl[4-(4-azidobutoxy)phenyl]azobenzene (EAPA), was synthesized and used to generate a novel polymer via step-growth polymerization using 1,3-dipolar cycloaddition reaction under the catalysis of CuSO₄·5H₂O/sodium ascorbate/H₂O (“Click” chemistry). The structure of the resultant main-chain azobenzene polymer, PEAPA, was characterized by GPC, ¹³C NMR, UV–vis and FT-IR spectra. Thermal stability and crystallinity of PEAPA powder were studied by TGA and WAXD. The photo-induced trans–cis isomerization of PEAPA and EAPA in N,N′-dimethyl formamide (DMF) solution was investigated. Furthermore, the thermal cis–trans isomerizations of PEAPA and EAPA were also observed at 60 °C in dark. Thermal stability and trans–cis–trans isomerization behavior of PEAPA was compared with its non-triazole analog, PDHA.     

Synthesis of stereo multiblock polylactides by dual terminal couplings of poly-L-lactide and poly-D-lactide prepolymers: A new route to high-performance polylactides

Poly-L-lactide (PLLA) having two anthracene (diene) terminals and poly-D-lactide (PDLA) having two maleimide (dienophile) termainals were prepared by the ordinary ring-opening polymerization (ROP) of L- and D-lactides with the corresponding functional initiators followed by the coupling reaction of the resultant terminal hydroxyls of the PLLA and PDLA prepolymers with hexamethylene diisocyanate (HMDI), respectively. The di-functional PLLA and PDLA obtained were then mixed and subjected to Diels–Alder coupling to spontaneously form PLLA-PDLA stereo multiblock copolymers (m-sb-PLA: PLLA-multi-PDLA) whose block sequences could readily be controlled by changing the molecular weight of the PLLA and PDLA prepolymers first synthesized by the ROP. The finally chain-extended m-sb-PLAs were found to have excellent thermal stability and thermo-mechanical properties because of the easy formation of stereocomplex crystals of PLLA and PDLA by retaining high molecular weight. This synthetic method based on the dual terminal couplings can afford a convenient route to stereo block copolymers of PLLA and PDLA having excellent properties and processability.     

Chromium substituted copper ferrites via gluconate precursor route

CuFe_2−xCr_xO₄ spinel (0≤x≤2) powders were synthesized by a soft chemistry method—the gluconate multimetallic complex precursor route. The complex precursors were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, thermal analysis and Mössbauer spectroscopy. The oxide powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), IR, Raman and Mössbauer spectroscopy. It was shown that the structure, morphology and magnetic properties of the obtained spinel powders depend on the concentration of Cr³⁺ ion. The XRD of the chromium substituted copper ferrite powders calcined at 700 °C/1 h indicated the formation of a cubic spinel type structure for x=0.5, 1.0 and a tetragonal structure for x=0, 0.2, 2. The crystallite size ranged from 19 nm to 39 nm. The Mössbauer spectroscopy revealed the site occupancy of iron ions, relative abundance and internal hyperfine magnetic fields in both tetrahedral and cubic CuFe_2−xCr_xO₄ spinels.     

聚苯乙烯纳米棒的界面法合成

首次采用界面聚合法成功地合成了聚苯乙烯(PS)纳米棒,利用透射电镜(TEM)、扫描电镜(SEM)、选区电子衍射(SAED)、红外光谱(FT-IR)及凝胶渗透色谱(GPC)等技术对其形貌和结构进行了表征.考察了单体浓度、反应时间与温度及有机溶剂等对聚苯乙烯形貌的影响.结果表明,以甲苯作为有机相溶剂、单体浓度为1.70 mol/L、60 ℃下反应10 h时能够得到平均直径为20 nm左右的纳米棒.样品的选区电子衍射(SAED)图与等规聚苯乙烯(i-PS)单链单晶的六方点阵衍射一致,GPC测试表明产物相对分子质量较低,且其分布范围较窄.     

苯法生产己内酰胺新技术

简述了苯法生产己内酰胺的新工艺技术 ,指出采用环己烷仿生催化氧化或复合金属氧化物催化氧化生产环己酮、环己基过氧化物无碱催化分解成环己醇酮、钛硅分子筛催化环己酮氨肟化生产环己酮肟、烟酸多级重排或分子筛气相重排生产己内酰胺以及进行己内酰胺精制工艺改进是技术发展的方向。     

Thermally stable NLO poly(amide-imide)s via sequential self-repetitive reaction

A series of thermally stable side-chain second-order nonlinear optical (NLO) poly(amide-imide)s via sequential self-repetitive reaction (SSRR) have been developed. This SSRR is based on carbodiimide (CDI) chemistry. Three difunctional azo chromophores (DR19, NDPD and DNDA) were, respectively, reacted with excessive amount of 4,4′-methylene-diphenylisocyanate (MDI) to form poly-CDI, and subsequently trimellitic anhydride (TMA) was added to obtain an intermediate, poly(N-acylurea). Poly(N-acylurea) exhibits excellent organosolubility, which enables the fabrication of high quality optical thin films. Moreover, its moderate glass transition temperature (T_g) characteristic allows the NLO-active polymer to exhibit high poling efficiency. After in situ poling and curing process, N-acylurea moieties were converted to amide-imide structures via SSRR, and the T_gs of the polymers were elevated significantly up to 70 °C higher than that of the poly-CDI sample. Electro-optical coefficients, r₃₃ of about 5.2-25.2 pm/V at 830 nm were obtained. Good temporal stability (80 °C) and waveguide optical losses (3.8-6.6 dB/cm at 830 nm) were also obtained for these polymers.     

Synthesis and characterization of fluoropoly(amide–sulfonamide)s via polycondensation

Novel fluorine-containing polymers, fluoropoly(amide–sulfonamide)s were synthesized for the first time by polycondensation from β-hydroxytetrafluoroethanesulfonic acid sultone (TFE-sultone) and hexamethylenediamine. The chemical structures of the obtained F-PASAs were characterized by intrinsic viscosity measurements, GPC, FTIR, ¹H NMR, ¹⁹F NMR and element analysis in detail. Thermal properties and optical property of F-PASAs were investigated by DSC, DMA, TGA and UV–vis spectra, respectively. The investigation indicated that these functional fluoropolymers in which there are both amide and sulfonamide linkages along the polymer main chains possessed distinctive structure as well as unique properties such as thermal properties, clean and high transparency and compatibility with nylons.     

Photopolymerization of urethane dimethacrylates synthesized via a non-isocyanate route

Urethane dimethacrylate monomers were synthesized via a non-isocyanate route from the reaction of a urethane diol with methacrylic anhydride. The urethane diols were synthesized through the reaction of ethylene carbonate with 1,6-hexanediamine, 3-amino-1-propanol and 2,2-dimethyl-1,3-propanediamine. ¹H NMR, ¹³C NMR and FTIR spectroscopies confirmed the structure of the monomers. Elemental analysis confirmed the purity of the monomers. Photopolymerization of these multifunctional monomers was investigated with respect to polymerization rates and conversions using photoinitiated differential scanning calorimetry. Irgacure 651^® was used as an initiator at 2 mol%. Photopolymerization results indicate high peak polymerization rates, 0.09 s⁻¹ compared to 0.06 s⁻¹ for bis-GMA and 0.07 s⁻¹ for HDDMA polymerized under the same conditions. Overall bulk conversions were 70-78%, compared to 68 and 76% for bis-GMA and HDDMA, respectively.The methodology developed here utilizes diamines and amino-alcohols that are members of commercially available families possessing a large range of structures, thus allowing synthetic flexibility in obtaining new urethane dimethacrylates with desirable properties.