Liquid Adsorption Chromatography Separation of Star Poly(methyl methacrylate)s

Liquid adsorption chromatography, in combination with full adsorption–desorption and precipitation–redissolution techniques, is a powerful procedure for the fractionation of mixtures in the synthesis of star polymers. An easy separation of 4‐ and 6‐arm star poly(methyl methacrylate)s from their single arm precursors could be carried out by both procedures, with differences of separation efficiency also depending on the molecular weight of the precursor and the number of arms.

Size exclusion chromatograms of retained and eluted fractions obtained by liquid adsorption chromatography/full adsorption–desorption separation with a tetrahydrofuran/cyclohexane eluent system (53:47 wt.‐%) for a crude reaction mixture (dotted line) containing a 4‐arm star PMMA polymer and a single‐arm precursor (solid lines a and b, respectively).     

Poly(alkyl methacrylate) monolithic columns for HPLC

Several monolithic macroporous polymer sorbents (pore size 1–2 µm) based on alkyl methacrylates and ethylene glycol dimethacrylate as a cross-linking agent were prepared by free radical copolymerization in columns 3×150 mm. The influence of compositions of the reaction mixture and porogens and the nature of the alkyl radical in a mixture of monomers on the hydrodynamic and chromatographic characteristics of the monoliths was studied. The monoliths based on n-butyl methacrylate have rigid macroporous morphology and excellent hydrodynamic characteristics (flow rate up to 5 mL min^?1). The efficiency of separation of a mixture of benzene and its derivatives in the version of reversed-phase HPLC was shown to increase with an increase in the fraction of a lauryl methacrylate additive (LMA) in the reaction mixture. The maximum separation efficiency (number of theoretical plates (tp)) was 35 000 tp m^?1 for the monolith based on n-butyl methacrylate with 7% LMA in the reaction mixture.     

Poly(oxanorbornenedicarboximide)s dendronized with amphiphilic poly(alkyl ether) dendrons

Attaching dendritically branched side chains to each repeat unit of a linear polymer produces molecular building blocks of nanometer‐sized dimensions called dendronized polymers. The structure of these complex molecular architectures is highly tunable and, therefore, of interest for a wide range of potential applications. The first examples of dendronized polymers prepared by living ring‐opening metathesis polymerization of oxanorbornenedicarboximide macromonomers with poly(alkyl ether) dendrons are reported. Small‐angle X‐ray scattering experiments on bulk samples confirm that the diameter of the individual cylindrical polymers can be tailored by the choice of dendron generation or the length of the hydrocarbon peripheral group. Analysis of the SAXS data based on a core‐shell model indicates that although the diameter of the cylinder increases with generation, the size of the core does not change; this suggests that these dendrons only loosely encapsulate the polymer backbone. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3221–3239     

Poly(methyl methacrylate) Membrane: Dynamic Measurement of Concentrations During Water-Induced Phase Separation

The properties of membranes produced by nonsolvent-induced phase separation (NIPS) depend on the rate of mass transfer of mobile components. This paper reports the use of Fourier transform infrared-attenuated total reflectance (FTIR-ATR) using principle component regression (PCR) analysis to study the compositional change of polymer solution immersed into the water prior to the phase demixing. To correlate the compositional change with the macroscopic structure, the observation on the dynamics of NIPS is made by a low magnification optical microscope equipped with a video camera. The morphology of the films was also examined by scanning electron microscope. Acetone and N, N-dimethylformamide were chosen as solvents to present different behavior of poly (methyl methacrylate) (PMMA) solutions during the NIPS process. The ratio of solvent and nonsolvent exchange, flux ratio shows the mass transfer in the homogeneous polymer solution after immersion in a nonsolvent bath. The results show that the flux ratio ( ) is affected by solvents which probably affects the ultimate structures of the precipitated polymer.     

混合离子液体对聚甲基丙烯酸甲酯分子链缠结及松弛行为的影响

首先通过两步法合成了具有双咪唑环阳离子结构的离子液体(DIL),并将其与单咪唑环离子液体(MIL)进行混合以调控黏度变化,混合离子液体(ILs)的黏度符合对数混合规则且随温度变化呈现Arrhenius型流体行为.进一步通过动态流变、示差扫描量热(DSC)、电化学测试等方法研究了混合离子液体中DIL比例对聚甲基丙烯酸甲酯(PMMA)链缠结和松弛行为的影响,并讨论了PMMA/ILs体系热稳定性、玻璃化转变及离子电导率等的变化.结果表明,DIL独特的双咪唑环结构可与PMMA分子形成更多相互作用位点,从而导致凝聚缠结的形成,很大程度上限制了PMMA分子链的运动和松弛.随DIL含量增加,PMMA/ILs体系的松弛时间、热分解温度、玻璃化转变温度等参数均呈增大趋势,但其离子电导率有所损失,这与DIL较大的分子尺寸和运动能力有关.     

聚甲基丙烯酸甲酯/聚(苯乙烯-丙烯腈)共混体系相分离的特征动态流变响应

采用动态流变学方法,结合小角激光光散射(SALLS)测定,对聚甲基丙烯酸甲酯(PMMA)/聚(苯乙烯－丙烯腈)(SAN)共混体系的动态流变行为与相分离的关系进行了研究.发现在低频区域,时温叠加失效与共混物体系发生相分离有关,时温叠加失效温度T_b与用SALLS测定的浊点温度T_c一致,用低频区域动态储能模量G'与频率的关系[1gG'～lg(α_T)]偏离线性粘弹模型或时温叠加失效温度表征PMMA/SAN共混体系的相分离是有效的.     

HPTLC Separation of Homologous and Isomeric Poly(ethyleneamine)s

Abstract

A simple, reliable HPTLC method has been developed for analysis of poly(ethyleneamine)s (PEAs). Ethylenediamine and all dimeric, trimeric, and tetrameric PEAs are separated without prior derivatization. Treatment with fluorescamine and visualization under ultraviolet light detects each PEA in quantities as low as 100 ng.     

Miscibility of Halogen-containing Polymethacrylates with Various Poly(alkyl acrylate)s

The miscibility behavior of a series of halogen-containing polymethacrylates with poly(methyl acrylate), poly(ethyl acrylate), poly(n-propyl acrylate) and poly(n-butyl acrylate) was investigated by differential scanning calorimetry and for lower critical solution temperature (LCST) behavior. Poly(chloromethyl methacrylate), poly(1-chloroethyl methacrylate), poly(2-chloroethyl methacrylate), poly(2,2-dichloroethyl methacrylate), poly(2,2,2-trichloroethyl methacrylate), poly(2-fluoroethyl methacrylate) and poly(1,3-difluoroisopropyl methacrylate) are miscible with some of the poly(alkyl acrylate)s. Most of the miscible blends show LCST behavior. However, poly(3-choloropropyl methacrylate), poly(3-fluoropropyl methacrylate), poly(4-fluorobutyl methacrylate), poly(1,1,1,3,3,3-hexafluoroisopropyl methacrylate), poly(2-bromoethyl methacrylate) and poly(2-iodoethyl methacrylate) are immiscible with any of the poly(alkyl acrylate)s studied. © 1997 John Wiley & Sons, Ltd.     

Isospecific polymerizations of alkyl methacrylates with a bis(alkyl)Yb complex and formation of stereocomplexes with syndiotactic poly(alkyl methacrylate)s

Yb[C(SiMe₃)₃]₂ initiates the living polymerization of methyl methacrylate (MMA) at −78°C to give the polymer with M_n of 51.0×10⁴ (M_w/M_n=1.1) and high isotacticity (97%) in a quantitative yield. Mixing of the acetone solution of resulting polymer (M_n=16.3×10⁴) with the acetone solution of syndiotactic poly(MMA) (M_n=15.7×10⁴) prepared by the (C₅Me₅)₂SmMe(THF) initiator produces desired stereocomplex in high yield bearing very high T_m whose tensile modulus is higher than the respective isotactic and syndiotactic poly(MMA)s. Yb[C(SiMe₃)₃]₂ also generated isotactic (98%) poly[2-(dimethylamino)ethyl methacrylate] (DMEMA), and (C₅Me₅)₂SmMe(THF) affords the syndiotactic (97%) polymer in high yields. The combination of isotactic poly(MMA)-block-poly(DMEMA) (97/3) and syndiotactic poly(MMA)-block-poly(DMEMA) (97/3) provides the amphiphathic stereocomplex. In sharp contrast to the catalysis of Yb[C(SiMe₃)₃]₂ in toluene, the addition of THF or HMPA resulted in the formation of syndio-rich poly(MMA).     

远离临界组成的聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物共混薄膜表面相分离动力学

采用温控原子力显微镜方法,在线跟踪了远离临界组成聚甲基丙烯酸甲酯/苯乙烯-丙烯腈无规共聚物(PMMA/SAN)共混薄膜的表面相分离行为,并研究了其动力学规律。 结果表明,在SAN含量为70%的样品中观察到了表面相分离行为,其过程可分为早期、中期和晚期3个阶段,分别对应特征化的标度指数:早期结果验证了Cahn线性理论,即标度指数为零;中期相行为主要受“碰撞-扩散”机理控制,因此表现出1/3的标度指数;在相分离后期,流体动力学主导了相区的生长和归并行为,此时标度指数变为2/3。 我们的研究结果对于深刻理解高分子相行为具有积极作用,并将对高分子薄膜加工提供必要的指导。     

Impact of Charge Transfer Complex on the Dielectric Relaxation Processes in Poly(methyl methacrylate) Polymer

The impact of the charge transfer complex on the dielectric relaxation processes in free poly(methyl methacrylate) (PMMA) polymer sheets was investigated. The frequency dependence of dielectric properties was obtained over the frequency range 0.1 Hz–1 MHz at temperatures ranging between 303 K and 373 K for perylene dye and acceptors (picric acid (PA) and chloranilic acid (CLA)) in an in situ PMMA polymer. The TG/dTG technique was used to investigate the thermal degradation of the synthesized polymeric sheets. Additionally, the kinetic parameters have been assessed using the Coats–Redfern relation. The dielectric relaxation spectroscopy of the synthesized polymeric sheets was analyzed in terms of complex dielectric constant, dielectric loss, electrical modulus, electrical conductivity, and Cole–Cole impedance spectroscopy. α- and β-relaxation processes were detected and discussed. The σ(ω) dispersion curves of the synthesized polymeric sheets show two distinct regions with increasing frequency. The impedance data of the synthesized polymeric sheets can be represented by the equivalent circuit (parallel RC).     

An Observation on the Microphase Separation of Poly(methyl methacrylate)-block-Polystyrene Copolymer

The well-ordered structures of block copolymer formed by self-assemble have attracted much attention as potentially interesting optical materials, especially as photonic crystals1,2. In order to achieve desirable photonic crystal properties, the morphologies of block copolymers should be controlled, including obtaining the correct size of domains for the optical frequencies of interest and attainment of long-range domain order and appropriate orientation. We know that the morphology of one blo…     

Limited Fraction of Crystallized Side Chains in Bottlebrush Poly(n-alkyl methacrylate)s

Crystallinity of bottlebrush polymers due to side chain crystallization has been considered to be related to the length of the side chains only under the assumption of complete participation of crystallization by all side chains.Recent experimental results revealed that in poly(n-alkyl methacrylate)s a fraction of side chains could not crystallize due to constraints imposed by the trapped main chain entanglements and required expansion of main chain-main chain distance.This result renders the or...     

Modulation of the Photophysical Properties of Pyrene by the Microstructures of Five Poly(alkyl methacrylate)s Over a Broad Temperature Range

Pyrene fluorescence spectra have been recorded in five poly(alkyl methacrylate)s (where alkyl is ethyl butyl, isobutyl, cyclohexyl and hexadecyl) over a 20–400 K temperature range. The changes in the position and the full width at half maximum (FWHM) of the 0–0 emission band (peak I) have been correlated with the structural characteristics of the alkyl groups in the different relaxation regimes of the polymers to assess the degree of coupling of the excited singlet states with the polymer cybotactic regions. Data treatment of the peak I positions using an electron–phonon model indicates that longitudinal optical modes are involved, and that the magnitude of coupling depends on the polymer structure and follows the same trend as the glass transition temperatures. The same spectral parameters have been correlated also with “hole” free volumes from positron annihilation spectroscopy over temperature ranges which span the glass or melting transitions of the polymers. Reasons why free volume and FWHM measurements follow the same trends, and other aspects of the systems, are discussed.     

Photodimerization of Coumarin Functionalized Poly(alkyl Acrylate) and Poly(alkyl Methacrylate) Random Copolymers: Influence of Copolymer Composition on Photocrosslinking

Coumarin‐containing poly(alkyl (meth)acrylates) were prepared via 70–80% esterification of hydroxy‐containing acrylic copolymers, then solution cast into thin films and photocrosslinked via the dimerization of coumarin derivatives with UVA light. The coumarin‐modified polymers crosslinked upon exposure and exhibited gel fractions between 74 and 99%. Coumarin dimerization efficiency increased with higher polymer mobility at the irradiation temperature. The effects of light intensity and irradiation time in photo‐dimerized systems followed the Bunsen‐Roscoe reciprocity law indicating that coumarin photodimerization depended only on dose. Thus, low intensities are overcome with longer times. This is an important advantage over photoinitiated free radical crosslinking which depends on irradiation intensity to the ½ power.     

Poly(trialkylsilyl methacrylate)s: A family of hydrolysable polymers with tuneable erosion profiles

Polymers containing hydrolytically labile trialkylsilyl ester side groups were synthesised via a conventional and a controlled radical polymerization. The trialkylsilyl methacrylate monomer unit was chosen for its capacity to hydrolyse into basic, acid or sea water varying the hydrophilic character of the resulting polymer backbone with time. The hydrolysis or saponification reaction of the ester bond of the trialkylsilyl methacrylate was monitored through a ¹H NMR study showing the formation of siloxane side-products. Several copolymers and polymer blends were prepared as matrixes for controlled erodible systems. Their capacity to hydrolyse was demonstrated through SEM investigations with selective dissolution of free films containing hydrolysable copolymers and PMMA blends. Well-defined random and diblock copolymers with methyl methacrylate were investigated to show the effect of the microstructure on the erosion properties of the corresponding coatings. Poly(methyl methacrylate-b-tert-butyldimethylsilyl methacrylate) diblock copolymers synthesised through the RAFT process showed a better control of the erosion with a constant erosion rate over a long-time service in sea water at pH = 8.2. In addition, experiments showed that the erosion rate could be modulated by varying the molar proportion of hydrolysable side groups onto the copolymer backbone and the weight amount of copolymers mixed with PMMA in toluene solution.     

Poly(methyl methacrylate)s with pendant calixpyrroles: polymeric extractants for halide anion salts

Poly(methyl methacrylate)s containing pendant octamethylcalix[4]pyrrole subunits were prepared and demonstrated to be capable of extracting tetrabutylammonium chloride and fluoride salts from aqueous media.     

Branched and Self-Crosslinkable Poly(methyl methacrylate)s Prepared via One-Pot Synthesis in Aqueous Emulsion

An approach to the synthesis of highly branched vinyl copolymers containing thiol and C=C crosslinking groups is proposed. This method was exemplified by the emulsion copolymerization of methyl methacrylate (MMA) and 1,6-hexanediol diacrylate (HDDA) with 2-mercaptoethyl sulfide (MES) as chain transfer agent at 70°C with 4,4′-azobis(4-cyanovaleric acid) (ACVA) as the initiator. The resulting highly branched copolymers contain both thiol and acryloyl groups. The apparent M_w (by SEC) of the resulting copolymers increased with increasing ACVA concentration, whereas the pendent acryloyl and -SH groups decreased from 6.4% to 0.8% (relative to MMA units) and 45 ×10^?5 to 5 × 10^?5 mol/g, respectively. The copolymers of MMA could be self-crosslinked thermally or by exposure to UV irradiation. The gel fraction of the thermally treated samples decreased from 46% to 7.2%, with the increasing of ACVA in the polymer synthesis, while the gel fraction of UV irradiated samples changed only slightly around 70%.