Surface activity and micellar behavior of dimethylamino‐ and trimethylammonium‐ tipped oxyethylene–oxybutylene diblock copolymers in aqueous media

Surface activity and micellar behavior in aqueous media in the temperature range 20–50°C of the two block copolymers, Me₂N(CH₂)₂OE₃₉B₁₈, (DE₄₀B₁₈) and I^?Me₃N⁺(CH₂)₂OE₃₉B₁₈, (TE₄₀B₁₈) in the premicellar and postmicellar regions have been studied by surface tensiometry, viscometry, and densitometry. Where E represents an oxyethylene unit while B an oxybutylene unit. Various fundamental parameters such as, surface excess concentrations (Γ_m), area per molecule (a) at air/water interface and standard Gibbs free energy for adsorption, ΔG have been investigated for the premicellar region at several temperatures. The thermodynamic parameters of micellization such as, critical micelle concentrations, CMC, enthalpy of micellization, ΔH, standard free energy of micellization ΔG, and entropy of micellization ΔS have also been calculated from surface tension measurements. Dilute solution viscosities have been used to estimate the intrinsic viscosities, solute‐solvent interaction parameter and hydration of micelle. Partial specific volume and density of the micelle were obtained from the density measurements at various temperatures. The effect of modifying the end group of the hydrophilic block was investigated by comparing the behavior of trimethylammonium‐ and dimethylamino‐tipped copolymers, designated TE₄₀B₁₈, and DE₄₀B₁₈, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Water‐soluble/dispersible carbazole‐containing random and block copolymers by nitroxide‐mediated radical polymerisation

A series of carbazole‐containing water‐dispersible poly(acrylic acid)‐b‐(9‐(4‐vinylbenzyl)‐9H‐carbazole) block copolymers (poly(AA)‐b‐poly(VBK)) and water‐soluble poly(methacrylic acid‐ran‐(9‐(4‐vinylbenzyl)‐9H‐carbazole)) (poly(MAA‐ran‐VBK)) random copolymers were synthesised in a controlled manner (i.e. low polydispersities $(\overline {M_{{\rm w}} } /\overline {M_{n} } < 1.3)$ by nitroxide‐mediated polymerisation (NMP) using an SG1‐based alkoxyamine initiator, BlocBuilder. Poly(AA)‐b‐poly(VBK) block copolymers were most easily accessed by using poly(AA) in its protected form as the macroinitiator for the 9‐(4‐vinylbenzyl)‐9H‐carbazole (VBK) block. Controlled polymerisation of MAA was accomplished using an excess of 10 mol.% SG1 relative to BlocBuilder with VBK as controlling co‐monomer (initial molar feed content f_VBK,0 = 0.03–0.20) in dimethylformamide at 80°C. Poly(MAA‐ran‐VBK) copolymers with a final VBK molar composition of F_VBK < 0.30 resulted in water‐soluble copolymers. In addition, as macroinitiators, poly(MAA‐ran‐VBK)s were sufficiently pseudo‐living to reinitiate a second batch of monomer (90 mol.% methyl methacrylate with styrene) in organic solvent and by ab initio, surfactant‐free emulsion polymerisation. In both cases, low polydispersity, amphiphilic block copolymers resulted $(\overline {M_{{\rm w}} } /\overline {M_{{\rm n}} } < 1.3)$ . © 2012 Canadian Society for Chemical Engineering     

Structural characterization and thermal behaviour of block copolymers of polydimethylsiloxane and polyamide having trichlorogermyl pendant groups

Block copolymers having a pendant trichlorogermyl group as a part of polyamide segment? (CO? R′? CO? NH? Ar? NH? )_xCO? R′? CO? and polydimethylsiloxane of general formula [(? CO? R′? CO? HN? Ar? NH)_x? CO? R′? CO? NH(CH₂)₃SiO(CH₃)₂ ((CH₃)₂SiO)_ySi(CH₃)₂(CH₂)₃ NH? ]_n (where R′ = CH₂CH(GeCl₃), CH(CH₃)CH(GeCl₃), CH(GeCl₃)CH(CH₃); Ar = C₆H₄, (? C₆H₃? CH₃)₂, (? C₆H₃? OCH₃)₂, 2,5‐(CH₃)₂? C₆H₂, C₆H₄? O? C₆H₄) were prepared by a polycondensation reaction and characterized using CHN and Ge analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopy, thermogravimetric analysis (TGA) and molecular weight determination. They have a lamellar structure with weight‐average molecular weight in the range 1.21 × 10⁵–4.79 × 10⁵ g mol^?1. These copolymers display two glass transition temperatures and have an average decomposition temperature of 489 °C. TGA, FTIR and gas chromatography/mass spectrometry studies indicate that degradation of these block copolymers results in carbon monoxide, oligomeric siloxanes and polyamide fragments. They are thermally stable due to the hydrogen bonded interlinked chains of polyamide, while they absorb water due to the presence of Ge? Cl bonding. Copyright © 2010 Society of Chemical Industry     

Conducting block copolymers. Towards a polymer pn- junction

Summary The synthesis of polyphenylacetylene (1), polypentafluorophenylacetylene (2) and the block copolymer of 1 and 2 polyphenylacetylene-polypentafluorophenylacetylene (3) using a Rhodium catalysed living polymerisation reaction is presented. Photoelectron spectroscopy of thin films of the individual polymers using 50eV photons from a synchrotron allowed for the determination of the position of the the electronic energy levels, ionisation potentials and the vacuum level shift which indicated that the block copolymer organises at the gold substrate surface such that the fluorinated part of the copolymer extends towards the air interface. Pulse radiolysis time resolved microwave conductivity (PR-TRMC) allowed for the determination of the minimum carrier mobilities and the carrier lifetimes. The sum of carrier mobilities, _min, were respectively 5.2·10^–7, 6.3·10^–7 and 3.2·10^–7m² V^–1 s^–1 and the first half life, _1/2, was 2.0, 1.5 and 1.0 s in 1, 2 and 3. The study shows that it is possible to make conducting block copolymers by the rhodium catalysed polymerisation of arylacetylenes with different electronic energies that organises at the surface giving rise to electronic properties that approach analogy to the traditional inorganic semiconductor pn-junctions.     

Ionic Liquids Promoted the C-Acylation of Acetals in Solvent-free Conditions

The synthesis of a series of fourteen 4-alkoxy-1,1,1-trihalo-3-alken-2-ones (2,3) [CX₃COC(R²)=C(R¹)OMe, where X = Cl, F; R¹/R² = Me/H, Bu/H, i-Bu/H, Ph/H, Thien-2-yl/H, –(CH₂)₄–, –CH(CH₂)₄CH(CH₂)₂–] from the acylation reactions of acetals (1) with trichloroacetyl chloride or trifluoroacetic anhydride in the presence of equimolar amounts of pyridine and imidazolium based ionic liquid ([BMIM][BF₄] or [BMIM][PF₆]) is reported. The reaction time, yields and IL recyclation are also investigated and this method showed advantages over the methods described in the literature.     

Thermal transitions of ethylene-vinyl chloride copolymers and their blends

Differential Scanning Calorimetry (DSC) measurements were performed on a series of ethylene-vinyl chloride copolymers (E-V) prepared via reductive dechlorination of poly(vinyl chloride) with tributyltin hydride. The copolymers were identical in chain length and branching distribution; differing only in comonomer content, sequence distribution, and stereoregularity of adjacent —V— units. Extrapolation of glass transition temperatures, T_g, measured for our E-V copolymers to pure polyethylene (PE) predicted a T_g = ?85 ± 10°C for amorphous PE. E-V copolymers with greater than 60 mol percent —E— units exhibited melting endotherms from 20 to 128°C and degrees of crystallinity from 12 to 63 percent. The melting point depressions observed for our E-V copolymers were in agreement with Flory's theory, if the ? CH₂? CH₂ moiety is considered to be the crystallizable unit and the moiety is assumed to prevent the ? CH₂? CH₂? units attached on either side from being incorporated into the crystal. In general, the E-V copolymer blends with PE were incompatible, while those with PVC were compatible only for E-V copolymers with high V contents (>80 mol percent). Blends of the amorphous E-V copolymers were found compatible if their V contents differed by less than 15 mol percent, while blends where one or both E-V copolymers are crystalline were found to be incompatible. The properties of these copolymers will be discussed in terms of their microstructure.     

Synthesis by reactive processing of block copolymers of Nylon 6 / Poly (ether-esteramide)

Summary Block copolymers of nylon 6 with 10, 15 and 20% of poly (ether-esteramide) as elastomeric phase were synthesized by reactive processing. These materials are obtained by the anionic polymerization of -caprolactam in the presence of a linear prepolymer of poly (ether-esteramide) with a Grignard reagent. Differential Scanning Calorimetry (DSC), torque rheometry and formic acid test were used to characterize the obtained copolymers. The results showed that block copolymers of Nylon 6 were formed. The melting temperature and the crystallinity of the copolymer decreased when the elastomer phase content increased. Two Tgs appeared; the blocks of the copolymers were not miscible. We calculate the size of nylon 6 blocks for each composition. The physical-mechanical behavior was also studied. More flexible materials were obtained when the soft phase content in the copolymer was increased. The results of this work provide an important information for the synthesis of this kind of materials by reactive extrusion.     

Thermotropic Liquid Crystalline Polyesters with Rigid or Flexible Spacer Groups

Several different series of rigid and flexible polyesters with main chain liquid crystalline units were prepared and their properties were examined in relation to their structures. The first group of polymers were rigid aromatic copolyesters with mesogenic groups based on either chloro or methyl hydroquinone terephthalate units combined with varying amounts of different types of bisphenol terephthalate units The bisphenol comonomers used contained the structure: in which X was none, ? C(CH₃)₂? , ? CH₂? , ? O? , ? S? , and ? So₂? . It was observed that the bisphenols with the bulkier X group were more efficient in destroying thermotropic liquid crystallinity of the resulting copolymers. The second group of polymers studied were flexible polyesters consisting of various types of mesogenic units which were connected together by different lengths of polymethylene flexible spacers. The liquid crystalline behaviours of these polymers, particularly their transition temperatures, were correlated with their structures. A brief review of previous studies on the synthesis of thermotropic liquid crystalline polyesters is included.     

Isothermal crystallization of metallocene‐based propylene/α‐olefin copolymers

Isothermal crystallization and subsequent melting behavior of two propylene/hexene‐1 copolymers and two propylene/octene‐1 copolymers prepared with metallocene catalyst were investigated. It is found that γ‐modification is predominant in all copolymers. The Avrami exponent shows a weak dependency on comonomer content and comonomer type. At higher crystallization temperatures (T_c) the crystallization rate constant changes more rapidly with T_c and the crystallization half‐time substantially increases. Double melting peaks were also observed at high T_c, which is attributed to the inhomogeneous distribution of comonomer units along the polymer chains and the existence of crystals with different lamellar thicknesses. The equilibrium melting temperatures (T) of the copolymers were obtained by Hoffman–Weeks extrapolation. It was found that the T decreases with increasing comonomer content, but are independent of comonomer type, implying that comonomer units are excluded from the crystal lattice. Dilation of the crystal lattice was also observed, which depends on crystallization, comonomer content, and comonomer type. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 240–247, 2005     

Toughening and phase separation behavior of nylon 6–PEG block copolymers and in situ nylon 6–PEG blend via in situ anionic polymerization

We have prepared in situ molded products of morphologically different nylon 6/polyethylene glycol (PEG) copolymers and their blends via anionic polymerization of ε-caprolactam in the presence of several kinds of PEG derivatives using sodium caprolactamate as a catalyst and carbamoyl caprolactam derivative as an initiator. Three carbamoyl caprolactams, such as tolylene dicarbamoyl dicaprolactam (TDC), hexamethylene dicarbamoyl dicaprolactam (HDC), and cyclohexyl carbamoyl caprolactam (CCC), with different functionalities and activities were used. Phase separation behavior was investigated by dynamic mechanical thermal analysis (DMTA) and DSC during in situ polymerization and melt crystallization. The mechanical properties of these molded products were evaluated. PEG segments in the block copolymers showed amorphous characteristics, whereas a large fraction of unreacted PEG segments was crystallized in as-polymerized samples, except for the products obtained using the CCC activator. The presence of PEG derivatives retarded the crystallization of nylon 6 part during in situ polymerization as well as melt crystallization. However, PEG segments did not alter the crystalline structure of nylon 6, showing α-crystalline modification. The nylon 6–PEG–nylon 6 triblock copolymers showed the highest impact strength, whereas the nylon 6–PEG diblock copolymers and in situ nylon 6–PEG blends showed no improved toughness. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1285–1303, 1999     

Polymeric reagents: Part 1. Synthesis of polymer-anchored amines useful for curing epoxy resins

A range of polymers carrying amino-functions [NHEt, NHBuⁿ, NEt₂, NPr, N(CH₂CH₂CH₂NH₂)₂, NMeCH₂CH₂CH₂NH₂ or NEtCH₂CH₂CH₂ NH₂] has been synthesised via amination of styrene-vinylbenzyl chloride copolymers, poly(epichlorohydrin) and poly(2-chloroethyl vinyl ether), and via homopolymerisation and copolymerisation (with styrene) of (n-butyl)(vinylbenzyl)-ammonium chloride. Some of the polymers showed promise as curing agents for epoxy resins.     

Conductivity and structure of a polyamide/silver iodide nanocomposite

In this study, the structure and properties of an organic–inorganic composite material prepared from nylon 6 doped with fine particles of silver iodide (AgI) were examined. The preparation of the composite involved the complexation of nylon 6 with polyiodide ions such as I and I by immersion in an iodine/potassium iodide (I₂–KI) aqueous solution followed by reaction in a silver nitrate (AgNO₃) aqueous solution; this resulted in the in situ formation of β-AgI fine particles within the nylon 6 matrix. The AgI content formed in the composite was dependent on the immersion temperatures of the I₂–KI and AgNO₃ solutions. Lower solution temperatures resulted in larger amounts of AgI in the composite. This method readily provided a composite with a high content of AgI in nylon 6 and a conductivity of approximately 10⁻⁵ Ω⁻¹ cm⁻¹. In a uniaxially oriented nylon 6 matrix, AgI particles precipitated with anisotropic shape, which was caused by the orientation of the precursor polyiodide ions. The structure of the oriented composite provided the anisotropic conductivity. Additionally, the composite exhibited high antibacterial properties. The procedure used in this study is considered a unique method for the preparation of organic–inorganic composites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enantiopure Helical Ferrocene–Triazole–Quinone Triads: Synthesis and Properties

The copper(I)‐catalyzed (2+3) cycloaddition between azido (or azidomethylene) ferrocenes and enantiopure (P)‐14‐(p‐ethynylphenyl)‐[5]‐tetrahydro‐helicenequinone afforded ferrocene–triazole–quinone triads, whereas diazido ferrocenes gave rise to the corresponding double triads. In reactions with 1,1′‐diazidoferrocene, the use of CuI/CH₃CN or CuSO₄/sodium ascorbate/THF conditions allowed the divergent formation of an open chain dimeric structure or a 1,4‐diaza‐[4]‐ferrocenophane resulting from an intramolecular oxidative coupling of the two triazole units formed after the double cycloaddition process.

     

The synthesis of an isobutylene-α-methylstyrene block copolymer with olefinic head-group: (CH3)2C=CHCH2-PIB-b-PαMeSt

Summary The title head-functionalized block copolymer was synthesized by first preparing a polyisobutylene carrying a (CH₃)₂C=CH₂-head-group and -Cl end-group, and subsequently starting the block copolymerization of -methylstyrene from the -Cl terminus.7th in the series: Cationic Polymerization with Boron Halides.     

Morphological and Physical Properties of Triblock Copolymers of Methyl Methacrylate and 2‐Ethylhexyl Methacrylate

Summary: Triblock copolymers of methyl methacrylate (MMA) and 2‐ethylhexyl methacrylate (EHMA) [that is, poly(MMA–EHMA–MMA)] were prepared by an emulsion atom‐transfer radical polymerization. The relationships of their structural, morphological, and physical properties were investigated. The latex particles had core‐shell morphologies and the block copolymers experienced phase separation. Small latex particles with a low number of cores could deform and wet silicon‐wafer surfaces, but the deformation of large latex particles was restricted by the internal two‐phase morphology of the particles. Latex casting produced continuous pinhole‐free films, in which hard poly(MMA) (PMMA) cores of different latex particles merged and provided interparticle connections. The morphology of solution‐cast films depended on block composition, solvent type, and film thickness. For all the prepared polymer samples, thick films cast in toluene had poly(EHMA) (PEHMA) materials at air surface, whereas those cast in tetrahydrofuran had a sponge‐like PMMA surface structure. Thin toluene‐cast films from P(MMA–EHMA–MMA) with the block degrees of polymerization ( ) 200–930–200 showed spherical PMMA domains and those from 380–930–380 yielded a protruded worm‐like PMMA structure. The copolymer materials were coated on a glass surface for peeling tests. The films gave good hot‐melt adhesion properties when the of the PEHMA block was over 600. The peeling strength depended on the lengths of both PEHMA and PMMA blocks. The P(MMA–EHMA–MMA) sample with of 310–930–310 yielded the highest peeling strength of 7.4 kgf · inch^?1. The developed material is demonstrated to be a good candidate for a solvent‐free, hot‐melt, pressure‐sensitive adhesives for special‐purpose applications such as medical tapes and labels.

     

Structure and thermal behavior of nylon‐6/polytetrahydrofuran triblock copolymers obtained via anionic polymerization

The structure, crystallization, and phase behavior of nylon6‐b‐polytetrahydrofuran‐b‐nylon6 triblock copolymers synthesized via activated anionic polymerization have been studied. The composition, molecular weight of polytetrahydrofuran (PTHF) soft block, and type of polymeric activators (PACs) have been varied. Differential Scanning Calorimetry (DSC), Wide‐Angle X‐ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), and Polarized Light Microscopy (PLM) experiments have revealed that in triblock copolymers only the nylon‐6 component crystallizes while PTHF segments are amorphous. The soft blocks do not alter the spherulitic crystalline structure of nylon‐6 and hard blocks crystallize in the α‐modification. The degree of crystallinity decreases with increasing PTHF concentration. The phase behavior has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). Two different glass transition temperatures (T_g) for all samples have been observed. This indicates that nylon‐6 and PTHF segments are not molecularly miscible and the copolymers are microphase separated. The mechanical properties of the copolymers synthesized have been evaluated. Nylon‐6 copolymers with soft block concentrations up to 10 w/w %, exhibit improved notched impact strength in comparison to the nylon‐6 homopolymer, retaining relatively high hardness and tensile strength. All copolymers possess low water absorption and good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1448–1456, 2002; DOI 10.1002/app.10448     

Polymers with mesogenic elements and flexible spacers in the main chain: Aromatic-aliphatic polyesters

A new series of aromatic-aliphatic polyesters of general structure: R₁ = terphenyl, biphenyl, stilbene R₂ = (CH₂)_n; ? CH₂? C(Me)₂? CH₂? ;? CH₂;? C(Et)₂? CH₂? ; (CH₂? CH₂? O)_n CH₂? CH₂? has been synthesised. The existence of thermotrpic liquid crystalline phases has been shown by polarised light microscopy. The texture observations have suggested the existence of nematic, S_A or/and S_C phases depending on the chemical structure. The temperature of transition between the phases and, as a consequence, the range of mesomorphism are highly dependent upon the chemical structure. The clearing point is high, even for the longest aliphatic group, while the melting point is depressed.     

New fluorinated polysiloxanes containing an ester function in the spacer—II. Surface tension studies

The surface tensions of fluorinated polysiloxanes prepared by hydrosilylation of unsaturated perfluoroalkyl esters derived from undecylenic acid [CH₂?CH? (CH₂)₈? COO? CH₂? CH₂? R_F, with R_F = C₆F₁₃, C₈F₁₇, and C₈F₁₇? (CH₂)₁₀COO? CH₂? CH₂? CH?CH₂] by methylhydrodimethylsiloxane copolymers of various Si? H contents have been measured. The critical surface tensions, γ_c, and the solid surface tensions, γ^D_s, were deduced from n-alkane and water contact angle data. They decrease as the perfluoroalkyl graft content of the copolymers increases. Some of them, which are in the range of the lowest surface tension fluoro polymers known, are observed when the fluorinated segments are self-organized at the interface, i.e. when the polymers are mesomorphous or crystalline at room temperature.     

Studies on crystallization kinetics of nylon 6-polyoxypropylene-nylon 6 copolymers

The crystllization kinetics of anionic-prepared nylon6-poly(oxypropylene) 1000-nylon 6 (NPN) block copolymers containing 1.20 to 8.76 wt% poly(oxypropylene)(POP) were studied. The thermograms of isothermal and nonisothermal differential scanning calorimetry of NPN block copolymers obtained were used for the study. The Avrami equation was used to analyze the isothermal crystallization of NPN nylon block copolymers. The Avrami exponent n obtained in the temperature range of 180 to 200 °C was 2.0 to 2.5. It was not similar to that for nylon 6 reported in literature. The activation energies of crystallization for the nylon block copolymers were smaller than that of nylon 6, and showed a minimum with POP content. The equilibrium melting point increased as the POP content decreased. For the nylon block copolymers with lower POP content, the slopes of T_c vs. T_m plots were higher than the values reported elsewhere. The Ozawa plot was used to analyze the data of nonisothermal crystallization. The obvious curvature in the plot indicated that the Ozawa model could not fit our system well, and there was an abrupt change of the slope in the Ozawa plot at a critical cooling rate.     

A new imine ligand avoiding imine–enamine rearrangement and cyclometallation: Synthesis and coordination of Me3C6H2CH2NCHtBu

The new imine ligand (E)-2,4,6-Me₃C₆H₂CH₂NCH^tBu (1) has been prepared from 2,4,6-trimethylbenzylamine and trimethylacetaldehyde. In this imine, the ortho-positions of the benzyl group are blocked by methyl groups, and there are no β-hydrogen atoms susceptible for imine–enamine rearrangement. Thus, reaction with [PdCl₂(C₆H₅CN)₂] leads to the complex trans-[PdCl₂(2,4,6-Me₃C₆H₂CH₂NCH^tBu)₂] (2) that cannot undergo cyclopalladation. The single-crystal X-ray structure analysis of trans-[PdCl₂(2,4,6-Me₃C₆H₂CH₂NCH^tBu)₂] (2) confirms the trans-coordination of the imine ligands in this square-planar complex.