Tailor made liquid crystalline networks exhibiting a chiral smectic C (S C * ) mesophase via living cationic copolymerization

Summary Living cationic copolymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (15-8) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(15-8)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in the copolymer) containing methacryloyl side groups. The thermally crosslinked copolymers with X/Y=5/5 to 9/1 display an enantiotropic chiral smectic C (S _C ^* ) mesophase.This paper is part 28 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 27: V. Percec, Q. Zheng: Polym. Bull., previous paper in the issue     

Liquid crystalline networks via living cationic polymerization of 11-[(4-cyano-4′-biphenyl)oxy]undecanyl vinyl ether with 11-vinyloxyundecanyloxy methacrylate

Summary Living cationic copolymerization of 11-[(4-cyano-4-biphenyl)oxy]undecanyl vinyl ether (6–11) with 11-vinyloxyundecanyloxy methacrylate (16-11) leads to copolymers poly[(6–11)-co(16-11)]X/Y (where X/Y is the mol ratio between the two monomers in copolymer) containing methacryloyl side groups. All copolymers are crosslinked upon annealing via the thermal induced polymerization of their methacryloyl side groups. The copolymers with X/Y=6/4 to 9/1 lead after crosslinking to liquid crystalline networks exhibiting a S_A mesophase.This paper is part 26 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 25: H. A. Schneider, V. Percec, Q. Zheng: Polymer, submitted     

Impact of electron beam treatment on copolymers of polylactide and poly(trimethylene carbonate) in an air atmosphere

The effect of exposure of polylactide (PLA) and poly(trimethylene carbonate) (PTMC) statistical copolymers to ionizing radiation was studied by means of EPR spectroscopy. In addition, the influence of radiation-induced processes on thermal properties, miscibility of the components, weight average molecular weight (M_w) and number average molecular weight (M_n) were investigated for doses in the range of 0–200 kGy. In copolymers containing PLA and PTMC components in a ratio of 30:70 and 70:30 PLA radicals identified in the homopolymer under cryogenic conditions were dominant. This showed that PTMC radical centers either recombine or are transferred to PLA along the macromolecules. The results obtained for the non-irradiated and irradiated samples showed that the glass transition values measured by differential scanning calorimetry and calculated using the Fox equation were similar and indicated compatibility between the constituents of the tested copolymers and their miscibility. M_w and M_n changes measured by gel permeation chromatography were used to determine the radiation yield of scission G(S) and cross-linking G(X). In the case of PLA and PLA-rich copolymers, the difference between G(S) and G(X) with increasing dose increased, thus the chain scission predominated over cross-linking. For PTMC rich copolymer, the effect was opposite.     

Toward a more accurate and extensible colorimetry. Part VI. Improved weighting functions. Preliminary results

This Part VI is a progress report, with two motivations. (1) To publish the new method of extraction of weighting functions, and to show the demonstrated large reduction of tristimulus error in an array of ten disparate visually-matching pairs of white lights, and (2) to attempt to interest others in joining the work. The direct extraction of improved weighting functions (WFs) from an array of visually matching pairs of white lights is the subject of Part VI. This new approach is made necessary by our finding (Part I) that color-matching functions by either the Maxwell method or by the maximum saturation method lead to large errors (discrepancies) in computed chromaticities of pairs of visually-matching lights. Using spectral power distributions (SPDs) of 5 types from Part IV, eight observers make 5 strongly metameric visual matches to the same broadband reference white light, with 1.3° visual field and 70 cd/m² luminance of the reference white. Each of the resulting 5 SPDs is averaged over the 8 observers, and the 5 averaged SPDs are formed into 10 pairs (the five averaged visually-matching lights taken two at a time). Tristimulus values X, Y, and Z are computed for each member of each pair by the CIE 1931 weighting functions (color-matching functions) x , y , and z . Absolute ΔX, the tristimulus error (the difference between computed X1 and X2 of the visually-matching lights), is computed for each pair and summed over the 10 pairs, as are ΔY and ΔZ. The often-large 10-pair total tristimulus error TTE is computed for X, Y, or Z. For example TTE_X is the sum of the ten absolute ΔX's of the 10 pairs. Then x is progressively altered in spectral shape by an algorithm that on each iteration reduces TTE_X. Weighting functions y and z are altered in turn. Reduction to 1–3%, of the TTE initially associated with the CIE weighting function, is achieved in this preliminary work. The changes in shape of the resulting functions are discussed. The simpler term “weighting function” is used rather than “color-matching function” for these, and it is recognized that, when finally correct, these functions should represent the three spectral sensitivities of the normal human visual system. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 226–233, 1998     

Synthesis of Y‐shaped poly(N,N‐dimethylamino‐2‐ethyl methacrylate) and poly(trimethylene carbonate) from a new heterofunctional initiator

A new amphiphilic Y‐shaped copolymer, comprised of hydrophobic Poly(trimethylene carbonate) (PTMC) and hydrophilic Poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDMAEMA), was designed and synthesized by a combination of atom transfer radical polymerization (ATRP) and ring‐opening polymerization (ROP) using a new heterofunctional initiator, Br‐Init‐(OH)₂, bearing one initiation site for ATRP and two for ROP. At first, a new trifunctional core molecule bearing hydroxyl group and bromine moieties, Br‐Init‐(OH)₂, was synthesized via protection followed by esterification reaction of 5‐ethyl‐5‐hydroxymethyl‐2,2‐dimethyl‐1,3‐dioxane with 2‐bromoisobutyryl bromide and deprotection. In the presence of trifunctional core molecule, Br‐Init‐(OH)₂, target Y‐shaped miktoarm star copolymers, (PTMC)₂‐ b‐PDMAEMA, were successfully synthesized by sequence conducting the ROP of TMC and ATRP of DMAEMA. The Y‐shaped copolymers were characterized by ¹H NMR and GPC measurements. Subsequently, the self‐assembly behavior of these copolymers was investigated by dynamic light scattering method and transmission electron microscopy, which indicated that these amphiphilic Y‐shaped copolymers can self‐assemble into micelles and possess distinct pH‐dependent size in aqueous milieu. The results indicate that the amphiphilic Y‐shaped copolymers had the pH‐responsive properties similar to the expected PDMAEMA. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The solid state reaction between RhX(PPh3)3 and (η5-C5H4Me)W (CO)3X (X = Cl,Br, I)

Reaction between RhX(PPh₃)₃ (X = Cl, Br, I) and (η⁵-C₅H₄Me)W(CO)₃Y (Y = Cl, Br, I) occurs in both the solution and the solid state and leads to exchange of both CO/PPh₃ and X/Y between the two reactants.     

Komplikationen bei der Initiierung kationischer Polymerisationen mit Lewis-Säuren - Modellrechnungen an Antimon-(V)-halogeniden

Complications in the Initiation of Cationic Polymerizations by Lewis Acids - Model Calculations for Antimony(V)halogenids Quantum-chemical CNDO/2-calculations including geometry-optimization show that complex anions (X₅Sb-Z-SbY₅)⊖ are formed as a result of interaction between Lewis acids SbX₅ and anions SbY₅Z⊖ (X, Y, Z = F, Cl, Br). This interaction is very strong in the case of X, Z = F and Y = Br. When the complex anions decompose the simple anions with the greatest number of fluorine ligands are formed. The interaction between the two different Lewis acids SbX₅ and SbY₅ yields a random distribution of the ligands of both acids. During formation of the ions SbX₄⊕ and SbXY₅⊖ the anion with the greatest number of fluorine ligands is formed. The probability of the conversion Sb(V)-Sb(III) is higher for SbCl₅ than for SbCl₆⊖.     

Comparison of lantadenes content and toxicity of different taxa of the lantana plant

Three taxa of the lantana plant (Lantana camara var.Aculeata) I (white-pink), II (yellow-pink), and III (yellow-red)-differed in the content of lantadenes and compounds X, Y, and Z. Lantadene A, lantadene B, and lantadene C were the major lantadenes of taxon III. It contained small amounts of lantadene D. Taxa I and II contained very small amounts of lantadene A and lantadene B. Compounds X, Y, and Z were the major constituents of taxa I and II, and they constituted 59% and 92% of the total constituents in these taxa, respectively. Ingestion of lantana leaf powder of taxon III by male guinea pigs caused severe hepatotoxicity. Taxon I elicited mild hepatotoxicity in one out of six animals while taxon II was nontoxic. The biological and ecological significance of the presence of high amounts of compounds X, Y, and Z in taxa I and n is not known.     

Molecular adsorption of n-alkyl amines,carboxylic acids,and amides onto well-defined,polar organic surfaces

This paper details the formation of oriented monolayer films by the solution-phase adsorption of n-alkyl-chained adsorbates (CH₃(CH₂)_n-1Y) onto the polar surfaces of terminally-substituted self-assembled monolayers (SAMs; Au/S(CH₂)_mX). The polar tail groups (X and Y) of the adsorbate and SAM included amine, carboxylic acid, and amide groups, and the formation of the adsorbed monomolecular films on the SAMs relied on non-covalent interactions between X and Y. Highly organized monomolecular adlayers could be produced on the SAM surface that were as densely packed as the underlying alkanethiolate SAMs comprising the first layer. The quality of the adsorbed monolayers was related to the identities of the tail groups X and Y.     

Non-catalyzed addition of secondary phosphine chalcogenides to divinyl chalcogenides under solvent-free conditions

Secondary phosphine chalcogenides, R₂PX (R═(CH₂)₂Ph, Ph; X?=?S, Se), react with divinyl chalcogenides, (CH₂═CH)₂Y (Y?=?S, Se, Te), at the 2:1 molar ratio (80–82°C, 56–80?h) in the absence of both catalysts (initiators) and solvents to quantitatively afford the corresponding anti-Markovnikov diadducts. Even at the equimolar reactant ratio, the diadducts are the major products, though monoadducts are also formed. When Y?=?Te, vinylphosphine chalcogenides and metal Te are obtained, thus showing that divinyl telluride behaves as the vinylating agent.     

Star‐shaped POSS–methacrylate copolymers with phenyl–triazole as terminal groups,synthesis, and the pyrolysis analysis

Star‐shaped polyhedral oligomeric silsesquioxane (POSS)–methacrylate hybrid copolymers with phenyl–triazole as terminal groups had been designed and synthesized via sequential atom transfer radical polymerization (ATRP), azidation, and phenylacetylene‐terminated procedures, and the hybrid copolymers here could be denoted as POSS–(PXMA‐Pytl)₈, where X can be M, B, L, and S, represented four different methacrylate monomers, such as methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), and stearyl methacrylate (SMA), respectively. Thermal gravimetric analysis (TGA) and in situ Fourier transform infrared spectroscopy (FTIR) were applied for studying the thermal stability and degradation mechanism, and it was found that all of the POSS–(PXMA‐Cl)₈ and POSS–(PXMA‐Pytl)₈ copolymers exhibited excellent thermal stabilities, which had great potential in heat‐resistant material application. Different tendencies of decomposition temperatures at 5% and 10% weight loss (T₅ and T₁₀) dependent on the side‐chain length and terminal group species were investigated respectively. The longer alkyl side chains of the monomers, the lower thermal stabilities, and enhanced T₅ and T₁₀ were also shown with the introduction of phenyl–triazole groups instead of chlorine groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40652.     

Properties of biomineralized (CaCO3) PVP-CMC hydrogel with reference to its cytotoxicity

The authors focus on properties of biomineralized (CaCO₃) PVP-CMC hydrogel (designated as I–X) including cytotoxicity assay using primary mouse embryonic fibroblasts. The biomineralized samples (VII–X) showed >80% cell viability, was selected for further characterizations. FTIR and XRD indicate deposition of CaCO₃ within the PVP-CMC hydrogel matrix, SEM shows changes in morphology and pore diameter (VII and VIII: 1–12 µm; IX: 10–70 µm; X: 70–170 µm), TGA determines the decomposition scenario of CaCO₃, and tensile strength of samples (VII–X) ranged between 0.04 and 1.0 GPa, which practically corresponds to the modulus of cancellous bone.     

Effect of ZrO2 addition on in-vitro bioactivity and mechanical properties of SiO2–Na2O–CaO–P2O5 bioactive glass-ceramic

Herein, a multicomponent bioactive glass (0Z, 46SiO₂–30CaO–18Na₂O–6P₂O₅, wt.%) is prepared via melting. ZrO₂ is introduced into the bioglass using two different methods, and then three types of glass-ceramic bulks are manufactured using low-cost pressureless sintering. The effect of ZrO₂ addition on the bioactivity and mechanical properties of the bioactive glass-ceramic is assessed. The results indicate that the main crystalline precipitate from the bioactive glass-ceramic is Na₂Ca(Si₂O₆). The crystallisation ability of the 5Z glass-ceramic, bioactive glass-ceramic with ZrO₂ added during melting at high temperature, is reduced because ZrO₂ participated in the reconstruction of the glass network. Further, the ZrO₂ addition led to a low rate of cation release when soaked in simulated body fluid, indicating a decreased bioactivity. At the same time, the 5Y bioactive glass-ceramic, prepared by mixing YSZ particles with 0Z using ball-milling, possesses not only the highest mechanical strength (about twice the strength of 0Z) but also a high bioactivity. This study presents a promising method for the production of excellent bioactive glass-ceramic and a candidate (5Y) for the clinical applications where load bearing is required.     

Thermally reactive liquid crystalline copolymers based on 11-[(4-cyano-4′-biphenyl)oxy]undecanyl vinyl ether and 2-vinyloxyethyloxy methacrylate

Summary Living cationic copolymerization of 11-[(4-cyano-4-biphenyl)oxy]undecanyl vinyl ether (6-11) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(6-11)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in copolymer) containing methacryloyl side groups. Upon thermal crosslinking via the polymerization of their methacryloyl side groups, the copolymers with X/Y=5/5 to 9/1 lead to liquid crystalline networks displaying a S_A mesophase. These results have demonstrated that a shorter spacer in the reactive bifunctional monomer 16-2 than in the mesogenic 6-11 monomer leads to networks with broader range of mesomorphism than those derived from a reactive monomer containing a spacer length equal to that of the mesogenic monomer.This paper is part 27 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 26: V. Percec, Q. Zheng: Polym. Bull., previous paper in the issue     

Poly(butylene terephthalate) modified with ethoxylated bisphenol S with increased glass transition temperature and improved thermal stability

Novel copolyesters have been prepared by polycondensation and by melt mixing of poly(butylene terephthalate) with an ethoxylated bisphenol S. No side reactions occur during the synthesis of the samples, as proved by NMR analysis. The polyesters were examined by TGA and DSC. The insertion of the bisphenol S (sulfonyldiphenol) group significantly improved the thermal stability of the polymer. The thermal analysis carried out using DSC technique showed that the T_m of the copolymers decreased with increasing co-unit content, differently from T_g, which on the contrary increased, exceeding in some cases 100 °C, and crystallization rate decreased. A polymer containing only terephthalate moieties and ethoxylated bisphenol S has been prepared for the first time.     

Synthesis and chain extension of nitroxide‐terminated styrene–maleimide copolymers

Thermal radical copolymerization of styrene (S) and maleimide (MI) at 125°C in diglyme in the presence of 2,2,6,6‐tetramethylpiperidin‐1‐yloxyl radical (TEMPO) was studied. Mole fractions of maleimide in the feed, F_MI, varied in the range 0.1–0.9. A quasiliving reaction process proceeded yielding copolymers with a low polydispersity (M_w/M_n = 1.17–1.41). The found azeotropic composition, (F_MI)_A = 0.46, did not differ substantially from that (0.5) in the conventional radical S‐MI copolymerization. At a higher conversion or MI content in the feed, deactivation of the copolymer chains occurred. The obtained TEMPO‐terminated S‐MI copolymers readily initiated polymerization of styrene; chain extension of the macroinitiators took place, giving poly(S‐co‐MI)‐block‐poly(S) diblock copolymers. The synthesized copolymers containing S and MI units were characterized by elemental analysis, NMR spectroscopy, size‐exclusion chromatography, and differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1863–1868, 2004     

Soft X‐ray Ptychographic Imaging and Morphological Quantification of Calcium Silicate Hydrates (C–S–H)

Morphological details of calcium silicate hydrate (C–S–H) stemming from the hydration process of Portland cement (PC) phases are crucial for understanding the PC‐based systems but are still only partially known. Here we introduce the first soft X‐ray ptychographic imaging of tricalcium silicate (C₃S) hydration products. The results are compared using both scanning transmission X‐ray and electron transmission microscopy data. The evidence shows that ptychography is a powerful method to visualize the details of outer and inner product C–S–H of fully hydrated C₃S, which have fibrillar and an interglobular structure with average void sizes of 20 nm, respectively. The high‐resolution ptychrography image enables us to perform morphological quantification of C–S–H, and, for the first time, to possibly distinguish the contributions of inner and outer product C–S–H to the small angle scattering of cement paste. The results indicate that the outer product C–S–H is mainly responsible for the q^?3 regime, whereas the inner product C–S–H transitions to a q^?2 regime. Various hypotheses are discussed to explain these regimes.     

Synthesis of a high‐trans 1,4‐butadiene/isoprene copolymers with supported titanium catalysts

The copolymerization of butadiene (Bd) and isoprene (Ip) with a supported titanium‐triisobutyl aluminum catalyst system was studied. An analysis using differential scanning calorimetry, X‐ray diffraction, and ¹³C‐NMR spectra indicated that products with 25–60 mol % Bd units were random copolymers and that the melting temperatures and glass‐transition temperatures (Tg) were 30–40 and ?74°C (or thereabout), respectively, which were very similar to those of natural rubber. The chemical structure of these copolymers was characterized by a high‐trans 1,4‐configuration: the trans 1,4‐content of Ip units was greater than 98%, and the trans 1,4‐content of Bd units was greater than 90%. The reactivity ratio of Bd was greater than that of Ip (r_Bd = 5.7 and r_Ip = 0.17). The sequence distribution of the monomer units of the copolymers followed a first‐order Markov statistical model. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1800–1807, 2003     

Sulfur‐containing polymers: Effect of composition on melting behavior and crystallization kinetics of poly(butylene terephthalate)

The melting behavior and crystallization kinetics of poly(butylene terephthalate/thiodipropionate) (PBT) copolymers were investigated using the differential scanning calorimetry technique. Multiple endotherms typical of PBT were observed in the copolymers under investigation and were found to be influenced both by crystallization temperature (T_c) and composition. Wide‐angle X‐ray diffraction measurements permitted the identification of the crystalline structure of PBT in all the copolymers investigated. By applying the Hoffman–Weeks method, the equilibrium melting temperature of the copolymers was derived. Isothermal crystallization kinetics were analyzed according to Avrami's treatment. Values of the exponent n close to 3 were obtained, independent of T_c and composition, results in agreement with it being a crystallization process originating from predetermined nuclei and characterized by three‐dimensional spherulitic growth. The introduction of butylene thiodipropionate units was found to decrease the PBT crystallization rate. The heat of fusion (ΔH_m) was correlated to the specific heat increment (Δc_p) of samples of different degrees of crystallinity, and the results were interpreted based on there being an interphase, whose amount was found to increase as the sulfur‐containing unit content was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2003–2009, 2003     

Electrochemical synthesis and characterization of conducting copolymers of biphenyl with pyrrole

Copolymer films of biphenyl and pyrrole were synthesized by electrochemical polymerization. The influence of the applied potential used for the electropolymerization on the structure, morphology, electrical conductivity, and stability of the films was examined. From the analysis of the current–time curves, it was found that the growth of the copolymer films starts immediately. The films were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy–energy-dispersive X-ray analysis, and their electrical conductivity (σ), energy gap (E_g), and electrochemical stability were also determined. Based on the results, the copolymers were classified into three groups. The first includes the (PP-PPy)_0.80 copolymer synthesized at the lowest potential E_ox (0.80 V), having the highest ratio R (R = 0.35) of quinoid to benzenoid rings (calculated from FTIR), the highest value of σ (σ = 0.9 S/cm), the lowest E_g (E_g = 1.20 eV), and has compact morphology. The second group concerns the copolymers synthesized at higher potential (0.82 up to 0.86 V), having lower R (∼ 0.20), lower σ (below 0.4 S/cm), higher E_g (∼ 1.35 eV), and they are less compact with many pores. The third group includes the copolymers synthesized at even higher applied potential (0.88 and 0.90 V), having even lower R values (∼ 0.10), significantly lower σ (∼ 10⁻³ S/cm), even higher E_g (∼ 1.70 eV), and they are very porous. The applied potential during electropolymerization strongly affects the properties of the synthesized copolymers. Because of the combination of high conductivity, low energy gap, and partial solubility with significant electrochemical stability, these new copolymers are attractive candidates for many applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012