尿素催化合成乙酸-β-萘酯

以尿素为催化剂,采用乙酸酐和β-萘酚合成乙酸-β-萘酯.乙酸-β-萘酯合成的最佳工艺条件为:n(乙酸酐)∶n(β-萘酚)为1.2∶1,催化剂尿素用量占β-萘酚物质的量的10％,反应温度80℃,反应时间40 min,此条件下,收率达95.7％,催化剂可重复使用4次以上.     

两亲性接枝物CPE-g-AM-MAH的合成条件研究

采用悬浮溶胀法将丙烯酰胺(AM)、马来酸酐(MAH)与氯化聚乙烯(CPE)进行接枝反应,制备得到了两亲性共聚物(CPE-g-AM-MAH),用红外光谱对接枝物结构进行了表征,利用正交试验法讨论了氯化聚乙烯、马来酸酐、AM/MAH比率、引发剂对接枝率和接枝效率的影响.结果表明:各影响因素对接枝率的影响顺序为AM>CPE>...     

N-[(4-溴-3,5-二氟)苯基]马来酰亚胺合成

以马来酸酐和4-溴-3,5-二氟苯胺为原料,对甲苯磺酸为催化剂,甲苯/DMF为混合溶剂,采用溶剂共沸法,制备了N-[(4-溴-3,5-二氟)苯基]马来酰亚胺,用FTIR、1HNMR和13CNMR对产物进行了结构表征,并对合成工艺进行优化,所得适宜工艺条件(以4-溴-3,5-二氟苯胺38.6 mmol计):催化剂对甲苯磺酸用量0.877 8 g,n(马来酸酐)/n(4-溴-3,5-二氟苯胺)=1.2,胺化反应时间为1.5 h,环化反应时间为2 h,产率可达92.6%。     

Preparation of well‐defined block copolymer having one polystyrene segment and another poly(styrene‐alt‐maleic anhydride) segment with RAFT polymerization

Block copolymers, polystyrene‐b‐poly(styrene‐co‐maleic anhydride), have been prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization technique using three different approaches: 1‐phenylethyl phenyldithioacetate (PEPDTA) directly as RAFT agent, mediated polystyrene (PS) block as the macromolecular PS‐RAFT agent and mediated poly(styrene‐maleic anhydride) (SMA) block with alternating sequence as the macromolecular SMA‐RAFT agent. Copolymers synthesized in the one‐step method using PEPDTA as RAFT agent possess one PS block and one SMA block with gradient structure. When the macromolecular RAFT agents are employed, copolymers with one PS block and one alternating SMA block can be produced. However, block copolymers with narrow molecular weight distribution (MWD) can only be obtained using the PS‐RAFT agent. The MWD deviates considerably from the typical RAFT polymerization system when the SMA is used as the RAFT agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,characterization and use of polymer‐supported phase transfer catalyst in organic reactions

A polymer‐supported (PS) phase transfer catalyst, polyethylene‐g‐quaternary ammonium salt (PE‐g‐Q_N⁺), is prepared through a three‐step graft copolymerization of maleic anhydride (MAn) onto polyethylene (PE) by photochemical method using 1% benzophenone (Bz) as photosensitizer. Post grafted acid hydrolysis of polyethylene‐g‐maleic anhydride (PE‐g‐MAn) results in the preparation of PE‐g‐succinic acid which on further treatment with tetrabutylammonium bromide (TBAB) under basic conditions in tetrahydrofuran (THF) gives PE‐g‐Q_N⁺. Optimum conditions pertaining to maximum percentage of grafting have been evaluated as a function of concentration of maleic anhydride, amount of photosensitizer, and time of reaction. Maximum percentage of grafting (25%) was obtained using 3.57 mol of MAn and 0.5 mL of 1% Bz in 120 min. The PE and graft copolymers, PE‐g‐MAn, and PE‐g‐Q_N⁺ were characterized by FTIR Spectroscopy and thermogravimetric analysis (TGA). The ionic nature of quaternary ammonium salt, PE‐g‐Q_N⁺ has also been confirmed by conductance measurements. PE‐g‐Q_N⁺ reagent have been used successfully for polymerization, amidation, and esterification reactions. The products obtained were characterized by FTIR and H¹NMR spectral methods. The reagent was reused for the further reactions and it was observed that the polymeric reagent polymerize, amidate, and esterificate the compounds successfully but with little lower product yield. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Molar mass determination of poly(octadecene-alt-maleic anhydride) copolymers by size exclusion chromatography and dilute solution viscometry

The number average molar mass M_n of poly(octadecene-alt-maleic anhydride) (PODMA) copolymers calculated from data obtained by size exclusion chromatography (SEC) using a polystyrene (PS) calibration was found to be inaccurate. The use of SEC combined with dilute solution viscometry enabled a method to be developed using an iterative approach, which does not require knowledge of the Mark-Houwink constants for PODMA samples. A new calibration curve was constructed as a plot of molar mass M_u for PODMA. True number-average molar masses M_n (true) calculated using the new calibration are approximately twice the apparent molar mass M_n (app) based on a PS calibration for higher molar mass samples (>10?000 g mol⁻¹).     

Preparation and characterization of maleic anhydride-functionalized syndiotactic polystyrene

The free radical-induced grafting of maleic anhydride (MA) onto syndiotactic polystyrene (sPS) has been accomplished in the solution process by using 1,1,2-trichloroethane as solvent and dicumyl peroxide as free radical initiator. The amount of MA grafted on sPS was evaluated by a titration method. Grafted products separated from the reaction mixture were purified and analyzed. Fourier transform infrared spectroscopy and ¹H NMR studies indicate that MA attaches to the sPS in the form of single succinic anhydride rings as well as short oligomers. The results obtained by GPC analysis suggest that the degradation and chain extension reaction do not occur under the reaction conditions. Moreover, the crystallization behavior of MA-functionalized sPS was also studied by means of differential scanning calorimetry. It was found that the crystallization behavior of the grafted polymer exhibited somewhat differences in comparison to the neat sPS. The MA-functionalized sPS crystallizes at higher rate than the unmodified polymer, on the other hand, the degree of crystallinity (X_c) are lowered by the presence of the MA grafts.     

Interfacial adhesion reaction of polyethylene and starch blends using maleated polyethylene reactive compatibilizer

The interfacial reaction of the polyethylene (PE)/starch blend system containing the reactive compatibilizer maleated polyethylene (m‐PE) was directly characterized by Fourier transform infrared (FTIR) spectroscopy. A significant amount of anhydride groups on m‐PE existed as hydrolyzed forms, resulting in a large amount of carboxyl groups. Using a vacuum‐heating‐cell designed in the laboratory, the carboxyl groups were successfully transformed into the dehydrolyzed state (i.e., anhydride group). This result enabled the direct spectroscopic observation of chemical reaction occurring at the interface. For the PE/starch blend system containing m‐PE, the chemical reaction at the interface was verified by the evolution of ester and carboxyl groups in the FTIR spectra. The effect of the reactive compatibilizer on the interfacial morphology was also examined by scanning electron micrography (SEM). Enhanced interfacial adhesion was clearly observed for the blend system containing reactive compatibilizer. Tensile strengths of blend systems containing m‐PE also increased noticeably compared with the corresponding system without compatibilizer. A similar observation was made for the breaking elongation data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 767–776, 2002     

Toughening of cycloaliphatic epoxy resins by poly(ethylene phthalate) and related copolyesters

Poly(ethylene phthalate) (PEP) and poly(ethylene phthalate–co‐ethylene terephthalate) were used to improve the brittleness of the cycloaliphatic epoxy resin 3,4‐epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate (Celoxide 2021?), cured with methyl hexahydrophthalic anhydride. The aromatic polyesters used were soluble in the epoxy resin without solvents and effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt % PEP (MW, 7400) led to a 130% increase in the fracture toughness (K_IC) of the cured resin with no loss of mechanical and thermal properties. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 388–399, 2002; DOI 10.1002/app.10363     

Compatibility and thermal properties of poly(acrylonitrile–butadiene–styrene) copolymer blends with poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The mechanical and heat‐resistant properties of acrylonitrile–butadiene–styrene (ABS) binary and ternary blends were investigated. The relationship of compatibility and properties was discussed. The results show that poly(methyl methacrylate) (PMMA) and styrene–maleic anhydride (SMA) can improve the thermal properties of conventional ABS. The Izod impact property of ABS/PMMA blends increases significantly with the addition of PMMA, whereas that of ABS/SMA blends decreases significantly with the addition of SMA. Blends mixed with high‐viscosity PMMA are characterized by higher heat‐distortion temperature (HDT), and their heat resistance is similar to that of blends mixed with SMA. For high‐viscosity PMMA, from 10 to 20%, it is clear that blends appear at the brittle–ductile transition, which is related to the compatibility of the two phases. TEM micrographs show low‐content and high‐viscosity PMMA in large, abnormally shaped forms in the matrix. Compatibility between PMMA and ABS is dependent on both the amount and the viscosity of PMMA. When the amount of high‐viscosity PMMA varied from 10 to 20 wt %, the morphology of the ABS binary blends varied from poor to satisfactory compatibility. As the viscosity of PMMA decreases, the critical amount of PMMA needed for the compatibility of the two phases also decreases. SMA, as a compatibilizer, improved the interfacial adhesiveness of ABS and PMMA, which results in PMMA having good dispersion in the matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2652–2660, 2002