Miscibility and Isothermal Crystallization Behavior of Poly (Butylene Succinate-co-Adipate) (PBSA)/Poly (Trimethylene Carbonate) (PTMC) Blends

Poly(butylene succinate-co-adipate) (PBSA)/poly (trimethylene carbonate) (PTMC) blend samples with different weight ratios were prepared by solution blending. The morphologies after isothermal crystallization and in the melt were observed by optical microscopy (OM). Differential scanning calorimetry (DSC) was used to characterize the isothermal crystallization kinetics and melting behaviors. According to the OM image before and after melting, it was found that the blends formed heterogenous morphologies. When the PTMC content was low (20%), PBSA formed the continuous phase, while when the PTMC contents was high (40%), PBSA formed the dispersed phase. The glass transition temperatures (T_g) of the blends were determined by DSC and the differences of the T_g values were smaller than the difference between those of pure PBSA and PTMC. In addition, the equilibrium melting points were depressed in the blends. According to these results, the PBSA/PTMC blends were determined as being partially miscible blends. The crystallization kinetics was investigated according to the Avrami equation. It was found that the incorporation of PTMC did not change the crystallization mechanism of PBSA. However, the crystallization rate decreased with the increase of PTMC contents. The change of crystallization kinetics is related with the existences of amorphous PTMC, the partial miscibility between PLLA and PTMC, and the changes of phase structures.     

Intermolecular Hydrogen Bonding of Poly(Imino Imino Ketone Ketone)

Molecular dynamics calculations were made of the distance from the hydrogen atom of the imino group to the distance of the oxygen atom of the carbonyl group of poly(imino imino ketone ketone) (PIIKK). The results showed that theoretically there was hydrogen bond formation between the hydroxyl group and the carbonyl group of PIIKK. The existence of the hydrogen bonding between the polymer chains of PIIKK was confirmed by infrared spectrum analysis. Due to the existence of the hydrogen bonding, the glass transition temperature increased to 273°C from 143°C for poly(ether ether ketone) (PEEK).     

离子液体中聚氧化乙烯(PEO)相变过程中的氢键效应

我们把Flory-Huggins模型推广应用到聚合物/离子液体体系,研究聚氧化乙烯(PEO)在离子液体[EMIM][BF_4]中相变过程中的氢键效应,理论模型考虑了三种类型氢键(Ⅰ型:PEO-[EMIM]~+氢键,Ⅱ型:PEO-[BF_4]~-氢键和Ⅲ型:[EMIM]~+-[BF_4]~-氢键)的形成,分析了三种类型的氢键分数随温度、 PEO体积分数的变化.研究发现,三种类型的氢键分数随温度的升高而减少.在较小PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数轻微地减小;在较大PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数急剧减少.Ⅲ型氢键分数随着PEO体积分数的增加而急剧降低.由于三种氢键效应,第二维里系数A_2随温度的增加而减小.通过计算分析不同分子量的PEO在[EMIM][BF_4]中的相图发现,在PEO体积分数较低的条件下,Ⅰ型、Ⅱ型和Ⅲ型氢键是PEO相变的主要驱动力;在PEO体积分数较高的条件下,Ⅰ型和Ⅱ型氢键在PEO相变过程中起到主导作用.     

Isothermal Crystallization and Miscibility of Isotactic Polypropylene/Poly(cis-butadiene) Rubber Blends

Isotactic polypropylene/poly(cis-butadiene) rubber (iPP/PcBR) blends were prepared by melt mixing. Isothermal crystallization and miscibility for neat iPP and blends of iPP/PcBR were investigated by differential scanning calorimetry. The presence of PcBR remarkably affected isothermal crystalline behaviors of iPP. An addition of PcBR caused shorter crystallization time and a faster overall crystallization rate, meaning a heterogeneous nucleation effect of PcBR upon crystallization of iPP. For the same sample, the crystallization peak was broader and the supercooling decreased as the crystallization temperature increased. The Avrami equation was suitable to describe the primary isothermal crystallization process of iPP and blends. The addition of PcBR led to an increase of values of the Avrami exponent n, which we suggest was because the blends had a stronger trend of instantaneous three-dimensional growth than neat iPP. The equilibrium melting point depression of the blends was observed, indicating that the blends were partly miscible in the melt.     

Photoinduced Structural Changes in Poly(4-Vinyl Pyridine): A Luminescence Study

In the present work we show a way of controlling photoluminescence (PL) properties through photoinduced quasi-crystal formation in a system based on poly(4-vinyl pyridine) (P4VPy). Under UV irradiation at 380 nm, concentrated solutions of P4VPy in pyridine turn into gel. This phase transition results in changes in the optical properties of this polymer. The position of the PL maximum can be changed continuously from 440 to 480 nm during irradiation. After several minutes of UV irradiation a new red-shifted PL at 492 nm appears upon excitation by light of a wavelength corresponding to that of the initial PL maximum, which is also red-shifted during irradiation. Solutions of P4VPy in pyrimidine show similar behavior, but those in pyridazine do not exhibit such behavior. We have found that the reason for the observed changes in the electronic properties is a photoinduced directional ordering of polymer molecules in a special quasi-crystal formation. The process originates from a structural change in the side chain of P4VPy, namely, protonation of the polymeric pyridine after solvation. During irradiation, the polymeric pyridinium ion interacts with neutral polymeric pyridine molecules. Interchain interaction through hydrogen bonds lead to an electronic property change. We observed that the process of photoinduced sol-gel transformation is reversible. Mechanical perturbation or heating can convert the gel back to a fluid solution. The red-shifted PL is not observed, and the initial PL is blue-shifted to 450 nm and stays there.     

Fluorene-Based Poly(imino ketone) with Fluorine Atoms on the Side Chains as an Intelligent High-Performance Polymer

Abstract

Fluorene-based poly(imino ketone) with fluorine atoms in the side chains (PIKF-F), as an intelligent, high-performance polymer, was synthesized by the reaction of 4,4′-dibromobenzophenone and 9,9-bis(3-F-4-aminophenyl) fluorene via a palladium catalyzed C-N cross-coupling reaction. Its structure was characterized by means of FT-IR and ¹H NMR spectroscopy. The results showed a good agreement with the proposed structure. The molecular weights of the PIKF-F were measured by GPC (calibrated by polystyrene standards). The M_n and M_w values were 64,800 and 153,300, respectively. Thermogravimetric analysis and differential scanning calorimetry measurements showed that the polymer possessed good thermal stability with a high 10% decomposition temperature (450?°C) and a high glass transition temperature (T_g = 250?°C). The PIKF-F exhibited UV (ultra violet) absorption bands at 340–370?nm in NMP solution, while the fluorescence spectra showed maximum emission of PIKF-F at 498?nm in NMP solution. Both optical properties indicate the PIKF-F is of potential use as an organic photoelectric material. Additionally, due to its special conjugated system and the intramolecular hydrogen bonding (N–H···F), it was endowed with significantly strong photonic luminescence and the change of fluorescent intensity was reversible as the temperature was changed.     

Mechanical and Thermal Behavior of Blends of Poly(hydroxybutyrate-co-hydroxyvalerate) with Ethylene Vinyl Acetate Copolymer

Ethylene vinyl acetate copolymer (EVA), with vinyl acetate contents of 60% or 80%, was used to improve the mechanical properties of poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV). Blends of PHBV/EVA were prepared with the ratios of 90:10, 70:30, and 50:50. Stress–strain results indicated that the tensile strength, elongation at break, Young's modulus, and toughness of PHBV blends could be adjusted by changing the composition of blends and miscibility. It was found that high elongation at break, ca. 200%, was obtained for PHBV/EVA80 (50:50).     

Effect of Solvent on the Miscibility of Polystyrene/Poly(Styrene-Co-Acrylonitrile) Blends at Different Temperatures

The effect of solvent and temperature on the miscibility of polystyrene (PS) and poly (styrene-co-acrylonitrile) (PSAN) was examined by the dilute-solution viscometry (DSV) method. The extent of miscibility of different PS/PSAN blend compositions (30/70, 50/50, and 70/30) in chloroform (CHCl₃) and N, N- dimethyl formamide (DMF) was discussed in terms of the signs of various viscosity (ΔB, μ, Δ[η], α, and β) parameters. Based on the sign convention of these interaction parameters, partial miscibility in DMF and almost immiscibility in CHCl₃ was indicated for the examined blend. The data obtained from the DSV method were then correlated with the ones obtained through density and refractive index measurements; good agreement was obtained. The study also revealed a relatively greater influence of temperature and composition on the miscibility of the blend in DMF than in CHCl₃.     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Miscibility and Crystallization Behavior of Poly (Ethylene Terephthalate)/Phosphate Glass Hybrids

Fundamental studies on miscibility and crystallization behavior of poly (ethylene terephthalate) (PET) and inorganic phosphate glass (Pglass) hybrids were conducted. The Flory–Huggins interaction parameter (χ) value of ?0.075 for the PET/Pglass hybrids was obtained using the Nishi–Wang equation, demonstrating that the Pglass and PET components were miscible in the melt state. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed the phase separation occurred during quenching from the melt. The phase boundaries between PET and Pglass were blurred, which indicated partial compatibility of the components in the solid state. Contact angle measurements indicated the interfacial tension of PET/Pglass hybrids was 1.5 mN/m, and the work of adhesion was 78.0 mN/m at 28 °C. Based on the Hoffman–Lauritzen theory, the nucleation constant (K_g) and fold surface free energy (σ_e) of PET/Pglass hybrids were less than those of neat PET.     

含萘环聚芳醚酮类聚合物的分子设计与性质研究

聚芳醚酮类聚合物由于具有优良的韧性、刚性、耐热等级高、电性能、耐辐射、耐疲劳、耐冲击、抗蠕变、耐磨、耐热水性好、阻燃性好等特点,在热塑性聚合物领域占有极其重要的位置. 其在航空、航天、核能、信息、通讯、电子电信、石油化工、机械制造、交通运输等高技术领域得到了成功的应用,使许多行业的传统产品实现了更新换代. 但是,随着世界新科技革命的蓬勃发展,对高性能结构材料提出了日益广泛而迫切的需求. 为进一步提高聚芳醚酮类聚合物的性能,满足某些特殊情况下的使用要求（例如高温、高辐照强度）,可考虑对它们进行交联. 使之可用热塑性材料的加工方法加工,然后通过热处理使其交联,成为热固性材料. 这就要求在聚合物链上引入可交联基团. 常用的脂肪族交联基团的引入,会导致聚芳醚酮耐热性降低,而只能寻找芳香族可交联集团的聚合物材料. 本论文的目的是从分子结构设计的角度出发,从合成新型单体入手,采用芳香族亲核取代路线,将萘环引入聚合物主链,合成出一系列的新型含萘环聚芳醚酮类聚合物,并在不同条件下对它们进行了热处理. 主要利用电子自旋共振（ESR）这一手段对热处理前后的聚合物进行了表征,研究了聚合物的热交联行为,讨论了萘环的化学环境、键连位置及热处理条件对交联反应的影响,建议了交联机理.  我们首先通过1,5-萘二酚(1, 5-DHN)、对苯二酚(HQ)和4,4′-二氟二苯酮（DFB）合成了新型高分子量的含1,5-萘二醚型聚醚醚酮无规共聚物（1, 5-PENEK）,发现随着萘环含量的增加, 聚合物的玻璃化转变温度升高,熔点和结晶能力逐步下降直至消失,力学性能略有下降但基本保持了聚芳醚酮的优良性能. 这些性质的改变是由于萘环的引入在增加了聚合物的刚性同时也降低了聚合物的有序排列能力所致. 通过DSC、WAXR检测发现,1,5-萘二醚型聚醚醚酮共聚物（1, 5-PENEK）在320 ℃以上空气中处理时发生交联反应. 随着萘环含量的增加及处理温度的提高,聚合物的玻璃化转变温度增高速度加快,结晶性能迅速下降. 当处理前后的样品用ESR定量检测时,发现只存在一个单峰,并且其幅度随着热处理时间的增加而增强. 增加微波功率时发现在谱峰的两侧有很弱的突起,采用微波功率饱和特性方法证实样品中存在两种性质不同的R₁和R₂自由基. 在不同气氛下处理该样品, 从它们ESR谱的特征推测：R₁可能是RO·自由基,采用改变ESR的检测温度的方法进一步确认热处理后的聚合物中R₁自由基是RO·自由基,并且经计算证明RO·自由基是与分子链中萘环相关联的. 我们又通过模拟的方法证实R₂自由基是萘环自由基. 通过作RO·自由基、萘环自由基的自旋浓度随热处理时间变化曲线发现两种自由基都参与了交联反应,只是RO·自由基的浓度明显高于萘环自由基,在交联反应中起主导作用. 两种自由基浓度随热处理时间的变化趋势相同,即在热处理前期自由基浓度随时间增长很快,中期则变化不大,而后呈线性增长. 可以认为,热处理前期,主要是自由基的激发过程,而中期生成的自由基大多以双基终止的方式被消耗掉,对浓度增长没有明显贡献. 玻璃化转变温度与此相反的变化趋势支持这一结论. 恒温热失重实验表明,1, 5-PENEK在340 ℃热处理时出现明显的分解,说明1, 5-PENEK在340 ℃发生的热交联反应是裂解交联反应. 通过以上测试结果,得到了含1,5-萘二醚型聚醚醚酮共聚物（1, 5-PENEK）在340 ℃热交联的反应机理.  第二部分,我们从1,4-萘二甲酸出发,经过酰氯化反应及付氏酰基化反应,合成了新型单体1,4-二（4-氟苯羰基）萘(1, 4-BFN). 并且利用所得到的单体和4,4′-二氟二苯酮（DFB）与对苯二酚（HQ）通过亲核取代反应合成了含1,4-萘环的聚醚醚酮酮共聚物（1, 4-PEEKNK）. 测试结果表明, 随着萘环含量的增加,1, 4-PEEKNK的玻璃化转变温度升高、 溶解性变好、熔点下降直至消失,1,4-PEEKNK均聚物的力学性能与PEEK相近. 经260 ℃以上热处理的1, 4-PEEKNK均聚物的热分析实验结果表明,随着处理时间或处理温度的增加, 玻璃化转变温度升高. 从而推断在空气中热处理时聚合物发生了交联反应. 结合FT－IR、NMR等提出,交联反应是发生在萘环上的交联反应. 我们同样采用了ESR技术对1, 4-PEEKNK聚合物的交联反应类型进行了研究. 发现自由基的浓度随着处理时间的增加同样经历了3个阶段,由此我们判断1,4-PEEKNK聚合物发生的交联反应为自由基交联反应. 在不同热处理温度下1, 4-PEEKNK聚合物处理8 h的自由基自旋浓度表明在260 ℃和300 ℃热处理时自由基浓度增加的很少,与未处理样品的浓度几乎一致,认为这是由于在此温度下自由基激发的速度相对缓慢, 因此自由基全部被用于交联反应. 但是在340 ℃热处理时,自由基的浓度则急剧增加,这说明在此温度下自由基产生的速度极快甚至也产生了其它种类自由基,虽然聚合物也发生了交联反应,但是有大量自由基剩余而不利于材料的进一步使用. 恒温热失重结果说明在260 ℃热处理的1, 4-PEEKNK未发生裂解反应. 通过以上结果,给出了1, 4-PEEKNK在260 ℃热交联的交联反应机理.  总之,我们合成了两种不同萘环化学环境及不同键连接方式的聚合物,对其基本性质进行了研究,并且发现两种聚合物在空气中于一定温度下热处理时都发生了交联反应,但交联方式及交联机理各有不同. 就综合性质及应用要求而言,我们认为1,4-萘二酮型聚合物PEEKNK作为全芳香性可交联聚芳醚酮类材料应具有很好的应用前景.     

Microstructures and Mechanical Properties of Poly(Trimethylene Terephthalate)/Maleic Anhydride Grafted Poly(Ethylene-octene)/Polypropylene Blends

A range of blends based on 70 wt% of poly(trimethylene terephthalate) PTT with 30 wt% dispersed phase were produced via melt blending. The dispersed phase composition was varied from pure maleic anhydride grafted poly(ethylene-octene) (POE-g-MA) over a range of POE-g-MA:polypropylene (PP) ratios. The micromorphology and mechanical properties of the ternary blends were investigated. The results indicated that the domains of the POE-g-MA are dispersed in the PTT matrix, and at the same time the POE-g-MA encapsulate the PP domains. The interfacial reaction between the hydroxyl-end group of PTT and maleic anhydride (MA) during melt blending changes the formation from “isolated formation” to “capsule formation,” where the PP domains are encapsulated by POE-g-MA. Compared to the PTT/POE-g-MA blends, mechanical properties of ternary blends, such as tensile strength and Young's modulus, were improved significantly.     

High-Pressure Analysis of the Multiple Melting Endotherms of Poly(ethylene succinate) and Poly(butylene succinate)

The origin of the multiple melting peaks in two linear polyesters, poly(ethylene succinate) (PES) and poly(butylene succinate) (PBS), of isothermally crystallized samples was investigated by differential scanning calorimetry (DSC) at atmospheric pressure and high-pressure differential thermal analysis (HP-DTA) at elevated pressures. In PES, the DSC melting curves showed three endothermic peaks at slow heating rates, which decreased to two with increasing heating rates. The HP-DTA curves showed that the area (qualitative) and peak height of the high-temperature peak decreased with increasing pressure and merged with the low-temperature peak at pressures above 450 MPa. This behavior supported the melting, recrystallization, and remelting model for the observed multiple melting endotherms. In PBS, the DSC melting curves were similar to those seen in PES. The HP-DTA curves were also similar to PES up to 400 MPa, but above this pressure the area and the peak height of the high-temperature peak and the temperature difference between the high- and low-temperature peaks remained unchanged. This observation suggested that the two peaks in PBS were due to the melting of two populations of crystals with different lamellar thickness originally present in the sample. The multiple melting behavior in isothermally crystallized PBS is proposed to incorporate both the melting of two populations of crystals and melting, recrystallization, and remelting.     

Investigation of Interpolymer Complexation Between Poly(Vinylcaprolactam) and Poly(Maleic Acid-Alt-Styrene)

The interactions between two synthetic polymers used in biomedical applications, maleic acid-styrene copolymer (MAc-St) and poly(vinylcaprolactam) (PVCL), were investigated in dilute aqueous solution considering the influence of the pH, the added salt and the ratio between the components in the mixture. Hydrogen-bonding interactions between the COOH groups of MAc-St and the C═O groups of PVCL, together with hydrophobic interactions are involved in the formation of the interpolymer complex. The complex is insoluble below pH = 2.85 in aqueous solution, but the addition of NaCl enlarged the pH domain where the precipitation of the complex occurred. When the ratio between the polymers was varied, two maxima of the optical density were obtained: at a 1:1 ratio between the COOH and caprolactam groups, and also at a lower ratio (1:3). Other investigations, like the measurements of the turbidity in situ during mixing, and fluorescence, viscometric and potentiometric measurements were performed in order to understand these interactions. The phase separation of the thermosensitive poly(vinylcaprolactam) in the presence of MAc-St was also studied. The cloud point and the phase transition profile were found to be influenced by the amount of polyacid, as well as by the pH.     

Miscibility,Crystallization, and Morphology of the Double-Crystalline Blends of Insulating Polyethylene and Semiconducting Poly(3-Butylthiophene)

A series of crystalline semiconducting poly(3-butylthiophene) (P3BT)/crystalline insulating polyethylene (PE) blends were prepared and the miscibility, crystallization, and structure/morphology were investigated. Even though phase separation was observed by transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS), several pieces of evidence indicated that limited miscibility should be present in PE/P3BT blends: small changes in both T_m and crystallinity of PE phase and a small portion of PE being dissolved in P3BT. The study of PE isothermal crystallization kinetics revealed that the introduction of P3BT significantly influenced the nucleation mechanism and growth geometry, i.e., PE was transformed from three-dimensional (3D) spherulitic to two-dimensional (2D) disc crystals. A striking reduction of nucleation density and an obvious ringed morphology of PE spherulites (2D) in PE/P3BT blends were also observed by polarized optical microscopy; it is proposed that the limited miscibility between PE and crystalline P3BT favors the formation of ringed PE spherulite in the blends. Additionally, preferred orientation of PE lamellae, with their b-axis largely constrained to the thin film plane, was observed by X-ray diffraction in PE/P3BT blend films. It is evidenced that the PE orientation was due to the b-axis being the crystal growth direction, which can only be in film plane.     

Fabrication and Characterization of Ultrathin Graphene Oxide/Poly(Vinyl Alcohol) Composite Films via Layer-by-Layer Assembly

Novel multilayer ultrathin films comprised of graphene oxide (GO) and poly(vinyl alcohol) (PVA) were fabricated through a layer-by-layer (LBL) assembly technique. GO could self-assemble onto quartz substrates alternately with PVA via hydrogen-bonding interactions. X-ray diffraction, atomic force microscopy, and transmission electron microscopy analysis revealed that GO was exfoliated to monolayers. The ultrathin films, with PVA/GO multilayer structures fabricated by LBL assembly, were characterized by ultraviolet-visible spectroscopy and X-ray diffraction analysis, confirming that the assembly of the multilayer films was quantitative and reproducible.     

Compatibilization of Poly(Trimethylene Terephthalate)/Polycarbonate Blends by Epoxy. Part 2. Melting Behavior and Spherulite Morphology

The melting behaviors of poly(trimethylene terephthalate)/polycarbonate (PTT/PC) blends, compatibilized by epoxy, and PTT spherulite morphology in the blends were investigated. When epoxy was present during blending, the melting behaviors of PTT/PC blends changed substantially; glass transition temperatures (T_g's) and cold crystallization temperature (T_cc's) of the PTT‐rich phase shifted to higher temperatures, while T_m's shifted slightly to lower temperatures, indicating that epoxy suppressed considerably all processes of dynamic movements pertinent to molecular (or segmental) movements. The cold crystallization process responded sensitively to thermal history. Changes of T_cc's with composition suggested that the epoxy's compatibilization effect was pronounced when PTT and PC were in near equal content.

Recrystallization or reorganization exotherms appeared before melting for isothermally crystallized PTT/PC and PTT/PC epoxy (E) blends. A wide angle X‐ray diffraction (WAXD) analysis showed that, although the perfection of PTT crystallites was influenced either by PC content and the presence of compatibilizer or by the crystallization temperature and crystallization time, PTT's crystal structure was independent of these variables.

The polarized light microscopy (PLM) observations showed that PTT spherulite morphology was very sensitive to blend composition. Epoxy addition interfered severely with the growth of PTT spherulites, causing them to be much less developed. When the spherulites grew under a condition of varied composition, they would exhibit diversified spherulite morphology, though in one spherulite.     

Morphology,Rheology, and Mechanical Properties of Polylactide/Poly(Ethylene-co-octene) Blends

Polylactide (PLA)/poly(ethylene-co-octene) (POE) blends containing ethylene-glycidyl methacrylate copolymer (EGMA) as a compatibilizer were prepared by melt blending. An immiscible, two-phase structure with POE dispersed in the PLA matrix was observed by scanning electron microscopy. It was found that the POE particle size was significantly decreased by the addition of EGMA, and the POE particle size and distribution decreased with the increase of the compatibilizer content up to 2% EGMA, beyond which the POE particle size and distribution remained unchanged. The reactions between the epoxy groups of EGMA and carboxylic or hydroxyl groups of PLA were elucidated by the Fourier transform infrared spectroscopy. Rheological results showed that the G′(ω), G″(ω), and complex viscosity of PLA/POE blends significantly increased at low frequencies with the addition of EGMA. The failure mode changed from brittle fracture of the neat PLA to ductile fracture of the PLA/POE blends.