bluuebunny/crossref_metadata_2025 huggingface dataset:
An intra‐individual quantitative assessment of acute laser injury patterns in facial versus abdominal skin
Authors: Bailey Steven H. , Brown Spencer A. , Kim Yeonsoon , Oni Georgette , Abtahi Fatemeh , Richardson James A. , Hoopman John , Barton Fritz , Kenkel Jeffrey M.
Published: March 2011

Introduction

Clinical laser settings have traditionally been calibrated on abdominal skin to predict and anticipate patterns of injuries in facial skin. This experimental approach has limitations as facial skin and abdominal skin have differences that may influence the depth of laser injury.

Objective

The primary objective of this study is to analyze the acute pattern of laser injury in abdominal skin and facial skin samples from the same subject and detail the anatomical and biophysical properties that can influence the laser tissue interaction. The secondary objective is to develop a conversion factor that will allow the prediction laser column depths in facial skin based upon laser column depths in abdominal skin.

Methods

Fifteen healthy subjects were consented and screened. Two 2 mm spots on the face and abdomen were identified and measured and treated with a fractional CO2 laser (Lumenis Ltd, Yokneum, Israel), with an energy setting of 15 mj, 300 Hz at a density of 10. Treatment areas were biopsied and analyzed histologically using hematoxylin and eosin and TUNEL staining.

Results

Facial skin and abdominal skin have several significant anatomical and biophysical differences (concentration of pilosebaceous units, sebum concentration, and moisture content). Facial tissue demonstrated divergence of laser energy around pilosebaceous units and lateral spread of laser energy along blood vessels. These differences cause attenuation (28%) of the laser energy and result in column depths that are significantly (P < 0.003) shorter in facial tissues (mean depth 415 µm) in comparison to abdominal tissues (mean depth 582 µm).

Conclusion

The variations in anatomic, biophysical, and biomechanical properties in facial skin cause an attenuation of the laser column depths in facial skin when compared to abdominal skin. A correction factor of 28% is required to predict the depth of laser columns in facial skin based on laser column depths observed in abdominal skin. Lasers Surg. Med. 42:99–107, 2011 © 2011 Wiley‐Liss, Inc.
Characterization of an optimized light source and comparison to pulsed dye laser for superficial and deep vessel clearance
Authors: Weiss Robert A. , Ross E. Victor , Tanghetti Emil A. , Vasily David B. , Childs James J. , Smirnov Mikhail Z. , Altshuler Gregory B.
Published: March 2011

Background and Objective

An arc lamp‐based device providing optimized spectrum and pulse shape was characterized and compared with two pulsed dye laser (PDL) systems using a vascular phantom. Safety and effectiveness for facial telangiectasia are presented in clinical case studies.

Study Design/Materials and Methods

An optimized pulsed light source's (OPL) spectral and power output were characterized and compared with two 595 nm PDL devices. Purpuric threshold fluences were determined for the OPL and PDLs on Fitzpatrick type II normal skin. A vascular phantom comprising blood‐filled quartz capillaries beneath porcine skin was treated by the devices at their respective purpuric threshold fluences for 3 ms pulse widths, while vessel temperatures were monitored with an infrared (IR) camera. Patients with Fitzpatrick skin types II–III received a split‐face treatment with the OPL and a 595 nm PDL.

Results

The OPL provided a dual‐band output spectrum from 500 to 670 nm and 850–1,200 nm, pulse widths from 3 to 100 ms, and fluences to 80 J/cm2. The smooth output power measured during all pulse widths provides unambiguous vessel size selectivity. Percent energy in the near infra‐red increased with decreasing output power from 45% to 60% and contributed 15–26% to heating of deep vessels, respectively. At purpuric threshold fluences the ratio of OPL to PDL vessel temperature rise was 1.7–2.8. OPL treatments of facial telangiectasia were well‐tolerated by patients demonstrating significant improvements comparable to PDL with no downtime.

Conclusions

Intense pulsed light (IPL) and PDL output pulse and spectral profiles are important for selective treatment of vessels in vascular lesions. The OPL's margin between purpuric threshold fluence and treatment fluence for deeper, larger vessels was greater than the corresponding margin with PDLs. The results warrant further comparison studies with IPLs and other PDLs. Lasers Surg. Med. 42:92–98, 2011 © 2011 Wiley‐Liss, Inc.
A clinical instrument for combined raman spectroscopy‐optical coherence tomography of skin cancers
Authors: Patil Chetan A. , Kirshnamoorthi Harish , Ellis Darrel L. , van Leeuwen Ton G. , Mahadevan‐Jansen Anita
Published: March 2011

Background and Objective

The current standard for diagnosis of skin cancers is visual inspection followed by biopsy and histopathology. This process can be invasive, subjective, time consuming, and costly. Optical techniques, including Optical Coherence Tomography (OCT) and Raman Spectroscopy (RS), have been developed to perform non‐invasive characterization of skin lesions based on either morphological or biochemical features of disease. The objective of this work is to report a clinical instrument capable of both morphological and biochemical characterization of skin cancers with RS‐OCT.

Materials and Methods

The portable instrument utilizes independent 785 nm RS and 1,310 nm OCT system backbones. The two modalities are integrated in a 4″ (H) × 5″(W) × 8″(L) clinical probe. The probe enables sequential acquisition of co‐registered OCT and RS data sets. The axial response of the RS collection in the skin was estimated using scattering phantoms. In addition, RS‐OCT data from patients with cancerous and non‐cancerous lesions are reported.

Results

The RS‐OCT instrument is capable of screening areas as large as 15 mm (transverse) by 2.4 mm (in depth) at up to 8 frames/second with OCT, and identifying locations to perform RS. RS signal is collected from a 44 µm transverse spot through a depth of approximately 530 µm. RS‐OCT data sets from a superficial scar and a nodular BCC are reported to demonstrate the clinical potential of the instrument.

Conclusion

The RS‐OCT instrument reported here is capable of morphological and biochemical characterization of cancerous skin lesions in a clinical setting. OCT can visualize microstructural irregularities and perform an initial morphological analysis of the lesion. The images can be used to guide acquisition of biochemically specific Raman spectra. The two data sets can then be evaluated with respect to one another to take advantage of the mutually complimentary nature of RS and OCT. Lasers Surg. Med. 42:143–151, 2011 © 2011 Wiley‐Liss, Inc.
Detection and management of latent tuberculosis in liver transplant patients
Authors: Jafri Syed-Mohammed , Singal Amit G. , Kaul Daniel , Fontana Robert John
Published: March 2011

The optimal means for detecting and managing liver transplantation (LT) patients with latent tuberculosis (TB) are not well defined. Our study aims were to (1) determine the frequency and risk factors of latent TB in a large cohort of consecutive adult LT candidates and (2) determine the safety and efficacy of isoniazid treatment in LT recipients with latent TB. A review of patients assessed for latent TB by skin testing using purified protein derivative (PPD; January 2004 to September 2008) or with the interferon-γ release assay QuantiFERON-TB Gold (QFT; March 2008 to October 2009) was undertaken. The baseline clinical features and outcomes of subjects with latent TB and subjects without latent TB were compared. Twenty-five of 420 subjects (6.0%) were positive for PPD. In comparison, 11 of 119 subjects (9.2%) had a positive QFT assay, and 15 others (13%) had indeterminate results. Both PPD-positive and QFT-positive subjects were less likely to be Caucasian than subjects without latent TB (p < 0.001). The 3-year survival rate of the 25 LT recipients with latent TB was similar to that of the 296 LT recipients without latent TB (78.7% versus 74.6%, P = 0.58). Fifteen of the 25 latent TB patients received isoniazid at a mean of 0.67 months after LT. Although isoniazid was discontinued in 8 subjects because of possible side effects, none of the 25 latent TB patients developed TB reactivation after transplantation with a mean follow-up of 33 months. In conclusion, both QFT testing and PPD testing demonstrate similar rates of detecting latent TB infection in American LT candidates, but QFT testing also leads to a moderate rate of indeterminate test results. Early isoniazid chemoprophylaxis after LT is poorly tolerated and is frequently discontinued. Liver Transpl, 2011. © 2011 AASLD.
Building high‐trust organizations
Authors: Shockley‐Zalabak Pamela S. , Morreale Sherwyn P.
Published: March 2011

This article presents a model for trust building in organizations that is both research‐based and practice‐driven; it is designed to help organizations produce the staying power that only trust can generate. The authors explain the five key drivers of trust: competence, openness and honesty, concern for employees and stakeholders, reliability, and identification.
Moving Up: Ten questions for leaders in transition (Part II)
Authors: Bruce Shaw Robert , Chayes Michael M.
Published: March 2011

Part I of this article (in Leader to Leader, No. 59, Winter 2011) discussed the four stages of a successful transition into a new leadership role, with a focus on an initial “discovery” phase. In Part II of the article, the authors discuss the questions that each new leader will need to answer in the remaining three transitional stages: Define: Mapping out key priorities and strategies; Deliver: Sustaining focus and ensuring progress; and Build: Building productive relationships with stakeholders.
Template polymerization by free radical mechanisms
Authors: Tan Y. Yong , Challa Ger
Published: March 2011

A polymerization in which propagation can proceed along macromolecular templates, is termed template polymerization. As compared to the blank (i.e. conventional) polymerization such a propagation, made possible through cooperative interaction, affects the kinetics of the reaction and the structural features of the formed (daughter) polymer. This is called template effect. Template systems can be classified according to the degree of monomer adsorption on the template which is characterized by the Langmuir equilibrium constant KM. In type I systems where KM = ∞ propagation proceeds exclusively by addition of adsorbed monomer arrays; in type II systems with KM = 0 propagation proceeds exclusively by addition of monomer molecules from solution. Such extreme cases are rare, however. Since most template systems have finite values between very large and very small, a generalized kinetic model for free‐radical template polymerizations has been developed from the type II model. Examples are given to illustrate the application of the generalized model. Some attention is paid to the structural features (average molecular weight and tacticity) of the daughter polymers, as well as to template copolymerization.
Microscopic kinetic events in emulsion polymerization
Authors: Napper Donald H. , Gilbert Robert G.
Published: March 2011

Experimental methods are reviewed which enable the microscopic kinetic events that underpin the formation of polymer latex particles and their subsequent growth in emulsion polymerizations to be explored. The growth of latex particles is the simpler of these two processes and considerable insight has now been gained into the mechanisms of the entry of free radicals into latex particles, the exit of free radicals therefrom, the fate of the exited free radicals and bimolecular termination events in the latex particles. Some progress has been made in modelling these processes theoretically. The formation of latex particles is a more complex phenomenon. The classical picture of latex particle formation occurring by the entry of free radicals into surfactant micelles appears to lack experimental substantiation. Particle size distribution results, which contain information about the rate of production of latex particles, imply that particles are generated by a multi‐step process which involves the coagulation of immature precursor particles. A semi‐quantitative theory for coagulative nucleation has been developed which predicts the general features of a broad range of nucleation phenomena.
Light‐induced cationic polymerization
Authors: Yagci Yusuf , Schnabel Wolfram
Published: March 2011

Mechanistic studies concerning the initiation of cationic chain reactions with the aid of diaryliodonium and triarylsulphonium salts are reviewed and recent results are presented. Laser flash photolysis in combination with pulse radiolysis experiments revealed evidence for a triplet path occurring parallel to the singlet deactivation route of electronically excited diphenyliodonium ions. The radical cations PhI+− and Ph2S+− were found to react selectively with nucleophiles, the former being more reactive than the latter. Moreover, various aspects of the photo‐initiated free radical‐promoted cationic polymerization of typical monomers such as tetrahydrofuran and butyl vinyl ether with the aid of acylphosphine oxides and other free radical initiators are discussed.
Cationic degradation of polysulfides and polyethers by chemical initiators and irradiation
Authors: Goethals E. J. , van Meirvenne D. , De Clercq R.
Published: March 2011

Degradation of polyacetals, polyoxiranes, polythiiranes, poly(ethylene disulfides) and poly(alkylene sulfides), initiated by cationic initiators, is a general phenomenom. The polyacetals lead to a mixture of monomer and cyclic oligomers; the polyoxiranes mainly to cyclic dimers. Cationic degradation of polythiiranes and poly(ethylene disulfides) leads to a variety of cyclic compounds the nature of which depends on the monomer substituents. Poly(alkylene sulfides) form the corresponding thiacycloalkanes. The mechanism of these degradations and the influence of substituents on the degradation products have been studied. Preliminary results on U.V. ‐ initiated cationic degradation of polythiiranes are reported.
Pseudo‐cationic polymerisation after 24 years
Authors: Plesch Peter H.
Published: March 2011

It is shown that the theory of pseudo‐cationic polymerisation is now well established. This is because it can account for old and new observations, including the living polymerisations initiated by Giusti's syncatalytic system (I2 + HI); and because attempts at disproving it have been unsuccessful. The theory's essential part is that in certain cationoid polymerisations the propagating species is an ester (which may be stabilised or activated), and that the propagation step involves the insertion of the monomer into a polarised covalent bond. It is made clear that the pseudo‐cationic theory is merely a generalisation of reaction mechanisms which are well known and uncontroversial in conventional organic chemistry. Ten experimental facts are analysed to show the relevance and plausibility of the pseudo‐cationic theory.

The two main versions of the “ions‐at‐any‐price” rival theories, namely the “large concentration of invisible ions” view and the “minute concentration of conventional carbenium ions” view are both shown to be incompatible with all the facts. It is emphasised that many industrial cationoid oligomerisations and polymerisations are pseudo‐cationic.
Living carbocationic polymerization XIV. Living polymerization of isobutylene with ester‐TiCl4 complexes
Authors: Kaszás Gabor , Puskás Judit , Kennedy Joseph P.
Published: March 2011

The living polymerization of isobutylene (IB) has been induced by cumyl acetate·TiCl4 and cumyl propionate·TiCl4 complexes in CH2Cl2/n‐C6H14 and CH3Cl/n‐C6 H14 mixtures under conventional laboratory conditions at −40°C. The living nature of the polymerization was demonstrated by linear M̄n versus Wp (g PIB formed) plots starting at the origin. DPn obeys [IB]/[cumyl acetate·TiCl4] and molecular weight distributions (MWD) are very narrow, M̄w/M̄n = 1.05–1.13. PIBs having M̄n >40000 have been prepared. The effects of the nature of the solvent, solvent composition, nature of the ester, ester/TiCl4 ratio and concentrations on rates, M̄ns and MWDs have been investigated. The living polymerization is faster by the cumyl acetate‐TiCl4 than by the cumyl propionate·TiCl4 complex. The rate of living polymerizations is negligible at CuAc/TiCl4 = 1 and increases significantly in the presence of stoichiometric excess of TiCl4 over the ester. Undesirable initiation due to protogenic impurities can be suppressed by employing relatively nonpolar (hexane‐rich) media, by increasing the ester/TiCl4, ratio, or by the addition of a non‐initiating ester (ethyl acetate); however, the rates decrease as a consequence of these measures. Polymerizations induced by mixtures of cumyl acetate·TiCl4/cumyl propionate·TiCl4 complexes yield monomodal narrow MWDs indicating rapid ester exchange at the growing site which in turn suggests ionic active species. The kinetic findings are explained by a mechanistic scheme that rests on two propositions: Propagation involves activated (most probably ionized) polymer‐ester·Lewis acid complexes, and free (uncomplexed) Lewis acid causes irreversible destruction of living propagation.
Macromonomers on the basis of 2‐phenyl‐2‐oxazoline
Authors: Schulz Rolf C. , Schwarzenbach Elmar
Published: March 2011

By initiation of the ring‐opening polymerization of 2‐phenyl‐2‐oxazoline (1) with p‐iodomethylstyrene a macromonomer with a styrene end‐group (2) is obtained. The degree of polymerization was varied between 10 and 16. The radical copolymerization of 2 with styrene is described. 1 forms with methyl triflate a very stable oxazolinium salt which is a good initiator for the bulk polymerization of 1 at temperatures of 50–70°C. It was conclusively proved that under these conditions the polymerization proceeds by a living mechanism. By termination with N, N‐dimethylaminopropylmeth‐acrylamide a macromonomer (5) was obtained. 5 can be radically homopolymerized. This comb‐like polymer 6 has the typical behaviour of a poly‐electrolyte and a polymeric amphiphile.
High‐conversion emulsion, dispersion and suspension polymerization
Authors: Adams Mary E , Casey Brendan S , Mills Martin F , Russell Gregory T , Napper Donald H , Gilbert Robert G
Published: March 2011

Some of the distinguishing features of emulsion polymerization kinetics at high conversion are discussed. The apparent anomaly that propagation rate coefficients deduced from bulk and emulsion systems at high conversion are greatly different actually arises because the initiator efficiency in the former is very low. At intermediate and at high conversions, termination kinetics must take account of the length of each terminating chain; data and a new theoretical model for this are found to be in accord. Modelling the reaction‐diffusion equations at high conversion (including new theory to account for polymer migration) shows that large (say, >200 nm radius) particles at high conversion will show strong spatial inhomogeneity (core‐shell structure) even in emulsion homopolymerizations, because of the slow diffusion of monomer and free radicals.
A kinetic and mechanistic study of the early stage of emulsion copolymerization of styrene and methyl methacrylate
Authors: Nomura Mamoru , Takahashi Koichi , Fujita Kazumi
Published: March 2011

Kinetic and mechanistic features in the early stage of the emulsion copolymerization of styrene and methyl methacrylate were examined using sodium lauryl sulfate and potassium peroxidisulfate as emulsifier and initiator, respectively. Experimental results on copolymer composition, molecular weight distribution, the rate of copolymerization and the number of polymer particles found in the early stage of the reaction showed that: (1) The amount of copolymers produced in the water phase decreases with an increase in the concentration of emulsifier initially charged and can be practically neglected above the critical micelle concentration(CMC), and hence, (2) Polymer particles are regarded to be produced mainly from the emulsifier micelles sufficiently above the CMC. (3) Coagulation of polymer particles can be neglected in the process of particle nucleation.
Modeling emulsion copolymerization: Crosslinking kinetics
Authors: Tobita H. , Hamielec A. E.
Published: March 2011

The authors' kinetic models for network formation in free radical polymerization both for pre‐ and post‐gelation periods are re‐examined and extended to include high mole fractions of divinyl monomer. Network formation in free radical polymerization is a non‐equilibrium process, namely, it is kinetically controlled, and therefore, the crosslinking density of a primary polymer molecule depends on its history. The crosslinking process is responsible for a distribution of crosslinking density with crosslinking density a function of the birth time of a primary polymer molecule. The crosslinking density distribution is an important feature of network formation in free radical polymerization. Under special rather limiting conditions the present kinetic models reduce to Flory's theory of network formation in which an equilibrium system is assumed. These kinetic approaches provide great insight into the phenomena of network formation, and they can readily be applied to emulsion polymerization.
Modeling of molecular weight distribution and microstructure of copolymers prepared in emulsion
Authors: Storti Giuseppe , Polotti Gianmarco , Canu Paolo , Carrá Sergio , Morbidelli Massimo
Published: March 2011

A stochastic model for evaluating Molecular Weight Distribution (MWD) and Chain Composition Distribution (CCD) of copolymers prepared in emulsion is applied to a “zero‐one‐two” binary system, i.e. with no more than two active chains per particle. Model predictions are compared with those by widely applied literature models based on bulk polymerization equations for evaluating CCD and on simplifying approaches for MWD (Refs. 5 and 6). For the particular system under examination, the range of reliable applicability of these approximated models is limited to high molecular weights (average degrees of polymerization larger than about 500 units), while for shorter chains the model here reported has to be used.
Dielectric characterization of latex suspensions by microwave spectrometry using mixture laws
Authors: David R. , Henry F. , Pichot C.
Published: March 2011

Mixtures of latexes and aqueous solutions of CaCl2, NaCl and KCl have been characterized by dielectric spectrometry in the microwave domain (at 5 GHz and at room temperature). The interpretation of the data was based on the concept of mixture laws applied for low concentrations of latex (< 10% in weight) and salt (concentration < 1 mol.1−1). The additivity of dielectric properties was in good agreement with that predicted using classical mixture laws.
Polymeric surfactants in emulsion polymerization
Authors: Piirma I.
Published: March 2011

The stabilizing efficiency of a variety of amphipathic copolymers was studied in aqueous emulsion polymerizations of styrene, methyl methacrylate and acrylonitrile. Using the number, and size of the particles as the criterion of stability, it was found that the availability for anchoring of the backbone in the amphipathic graft copolymers was crucial for stability. Within a system, a change in the backbone chain length with the same percent hydrophilic grafts had no effect on the outcome of the reaction: the latices stabilized to the same number of particles of the same size.

The results with the polystyrene‐block‐poly(ethylene oxide) copolymers as stabilizers in styrene polymerization gave indication that for efficient anchoring the block length need not be more than 10 monomeric units, and that a poly(ethylene oxide) (PEO) with weight‐average molecular weight Mw = 3000 is just as effective stabilizer as is a block with PEO of Mn = 9000.
Batch emulsion copolymerization of 50/50 vinyl acetate/ n‐butyl acrylate using poly(vinyl alcohol) emulsifier
Authors: Vanderhoff J. W. , Earhart N. J. , Dimonie V. L. , El‐Aasser M. S.
Published: March 2011

In the batch emulsion copolymerization of 50/50 vinyl acetate/n‐butyl acrylate mixture, no emulsifier or sodium lauryl sulfate emulsifier gave a n‐butyl acrylate‐rich copolymer until the n‐butyl acrylate became depleted, and a vinyl acetate‐rich copolymer and poly(vinyl acetate) thereafter, as expected from the disparate copolymerization reactivity ratios (r1 0.05; r2 5). In contrast, poly(vinyl alcohol) emulsifier gave an initial polymerization of vinyl acetate at a rate equal to or greater than that of the n‐butyl acrylate up to 7–37% conversion; then, the n‐butyl acrylate polymerized preferentially until it became depleted, followed by the remaining vinyl acetate, to give a vinyl acetate‐rich copolymer and poly(vinyl acetate), as expected from the copolymerization reactivity ratios. The mechanism proposed for this process comprised the grafting of vinyl acetate on the poly(vinyl alcohol) in solution to give a water‐insoluble graft copolymer, which precipitated and served as the locus for nucleation of poly(n‐butyl acrylate)‐rich particles. Fully hydrolyzed poly(vinyl alcohol) required a higher degree of grafting to give a water‐insoluble graft copolymer than partially hydrolyzed poly(vinyl alcohol).
Stereospecific and anionic ring‐opening polymerization
Authors: Spassky Nicolas
Published: March 2011

The polymerization features of the polymerization of heterocyclic monomers using anionic or coordinated anionic type initiators are examined. The chemical and configurational structure of initiating species depends on the regiospecificity of the ring‐opening reaction. Propagating rate constants, solvation and macrocyclisation phenomena are discussed. The structure and the chemical composition of stereospecific initiators are described. Different types of mechanisms (enantiomorphic sites and end‐chain) are illustrated. The dependence of selectivity on different parameters is discussed. Various aspects of chiral catalysis leading to stereoelective and enantiogenic processes are presented. Some examples of recent trends in anionic and stereospecific ring‐opening polymerization are given.
Use of cyclic carbonate oligomers in the synthesis of bisphenol‐a polycarbonate‐polydimethylsiloxane copolymers
Authors: Evans Thomas L. , Carpenter John C.
Published: March 2011

Polydimethylsiloxane‐polycarbonate block copolymers were prepared by sequential anionic polymerizations of cyclic carbonate oligomers and octamethylcyclotetrasiloxane, or by reaction of hydroxy‐terminated polydimethylsiloxane oligomers with cyclic carbonates or by reaction of hydroxy‐terminated polycarbonate oligomers (derived from cyclic carbonates) with chlorine‐terminated polydimethylsiloxane oligomers. The use of cyclic carbonates for making the copolymers afforded a synthetic flexibility not available through conventional methods involving phosgene.
Ring‐opening polymerization of cyclic ketene acetals and unsaturated cyclic spiro ortho esters
Authors: Bailey William J. , Gu Jia‐Ming , Lin Yin‐Nian , Zheng Zhi‐Feng , Zhou Lin‐Lin
Published: March 2011

Three new substituted cyclic ketene acetals and two unsaturated spiro ortho esters were synthesized. The free radical polymerization of cyclic ketene acetals gave zero or very low yields because of steric hindrance effects. However, cationic polymerization gave relatively high yields of polymers with predominant ring opening. Although the cationic polymerization of the spiro ortho esters produced mostly double ring‐opened polymers, their free radical polymerization yielded non‐ring‐opened polymers.
Functional oligomers of norbornene, 2 ‐ kinetics and mechanism of the oligomerization reaction
Authors: Cramail Henri , Fontanille Michel , Soum Alain
Published: March 2011

A comprehensive study of initiation and propagation steps of norbornene oligomerization initiated by WC16/Me4Sn in the presence of unsaturated diesters, was carried out. Kinetic orders, apparent rate constants and thermodynamic parameters were determined. Given the experimental results, a mechanism of both initiation and propagation reactions is proposed.
Ring‐opening metathesis polymerization and cyclic organoborane monomer
Authors: Chung T. C.
Published: March 2011

This paper summarizes our research result in the preparation of functional groups containing polyolefins, including linear and cyclic polymers, by using ring‐opening metathesis polymerization (ROMP) and cyclic organoborane monomers. Most organoborane moieties are very stable to metathesis catalysts. In turn, the borane containing polymers can be converted to a broad range of functional polymers with various functional groups, such as ‐OH, ‐NH2, ‐NHR, under mild conditions. With some pre‐designed monomers, several unique polymer structures, such as alternating copolymers have been prepared. In addition, the conformation of the polymer chain, from high cis double bonds to high trans ones, can be controlled by using various catalyst systems and reactions conditions. In this paper, we will also discuss some physical properties of the resulting polymers including thermal stability and chain conformations in selective solvents and at air‐water interfaces.
Synthesis, mechanisms. Kinetics and characterization of polyamic acid and polyetherimides
Authors: Grenier‐Loustalot Marie‐Florence , Joubert Frédéric , Grenier Philippe
Published: March 2011

We have synthesized a series of model compounds to study the polymerization mechanisms of polyamic acids prepared from a dianhydride and an aromatic diamine. Structural information (FTIR, liquid and solid (CPMAS) 13C NMR spectroscopy) obtained with model compounds has enabled the precise determination of the endchains (anhydride/amine acid ratios) in the polymers synthesized. In terms of reaction mechanisms, it was snown that the reaction path of dianhydride ring opening is such that the carbon atom bearing the carbonyl group on the benzene ring (meta from the bridge) preferentially undergoes nucleophilic attack and that the anhydride rings on the initial monomer can be considered to be independant. It was also shown that the reaction solvent has a very pronounced effect on the stereoselectivity of the reaction.
Aluminium‐27 NMR studies of aluminiumporphyrins
Authors: Desimone J. M. , Stangle M. , Riffle J. S. , McGrath J. E.
Published: March 2011

Aluminium‐27 NMR has been employed to study several different aluminiumporphyrins based on (5, 10, 15, 20‐tetraphenyl)porphyrin (TPPH2). The aluminiumporphyrins were formed by reacting a stoichiometric amount of trialkylaluminium with TPPH2to yield TPPAl‐R. The resulting aluminiumporphyrin was modified by adding a stoichiometric amount of various carboxylic acids to form aluminiumporphyrin carboxylates that had varying steric and electronic effects on the macrocycle.
Synthesis of rodlike polyhydrocarbons
Authors: Heitz W.
Published: March 2011

Stiff macromolecules are obtained by combining two aromatic units, either directly or by vinylene or ethynylene. The palladium‐catalyzed synthesis of poly(1,4‐phenylenevinylene), poly(1,4‐phenyleneethynylene), and poly‐p‐phenylene is described. Side reactions influencing the rodlike structure are investigated by model reactions.

Phenyl‐substituted poly‐p‐phenylene is obtained starting from phenyl‐1,4‐dibromobenzene. This is a solution and melt processable polymer that is stable up to 600°C. By anionic polymerization of 2‐phenyl‐1,3‐cyclohexadiene a precursor polymer with Mw/Mn = 1,1 can be obtained with molecular weights up to 30 000. By aromatization, poly(phenyl‐1,4‐phenylene) with a narrow molecular weight distribution is obtained. All of these polymers show thermotropic behaviour.

Poly(1,4‐pyridinium salts) are a new class of polymers. They are rodlike polycations. With large gegenions they are soluble in organic solvents.
Rotational barriers and chain dynamics
Authors: Allegra Giuseppe , Ganazzoli Fabio
Published: March 2011

Internal viscosity, or the high‐frequency viscous dissipation in polymer dynamics originating from the rotational energy barriers around skeletal bonds, is basically attributed to hindrance against the motion of conformational changes along the chain contour. The non‐equilibrium statistical‐mechanical background of the theory is discussed. Comparison between calculations and experimental results of the complex modulus and of the optical flow birefringence from polystyrene solutions under alternating shear stress is discussed. The best‐fitting value of the characteristic time for bond rotation τ0, i.e., the only parameter required for internal viscosity, is in good agreement with the results of NMR, ESR and dielectric relaxation experiments.
Degradable polyethylene‐starch complex
Authors: Albertsson Ann‐Christine , Karlsson Sigbritt
Published: March 2011

A biodegradable additive is often included in otherwise inert polymers in order to get a degradable material. Low density polyethylene (LDPE) containing starch in a masterbatch (MB) was degraded by photooxidation (UV). LDPE samples containing MB were more degraded than LDPE samples containing only starch. The MB contains a transition metal and an antioxidant thereby improving the total environmental degradation.
Shaping molecules and molecular architectures for linear and non‐linear optical properties
Authors: Wegner Gerhard
Published: March 2011

The linear and non‐linear optical (NLO) properties of novel macromolecular materials are described. Solid polyelectrolyte glasses exhibit high refractive indeces and excellent transmission at low dispersion. Polyconjugated macromolecules provide for materials with NLO‐properties interesting for χ(3)‐processes. The scaling behaviour of χ(3)∼λmax is demonstrated. Ultrathin layers of hairy‐rod type polymers are excellent objects to study wave‐guide related processes in organic systems.
Mesomorphic poly(diethylsiloxane) elastomers
Authors: Godovsky Yu. K. , Valetskaya L. A. , Papkov V. S.
Published: March 2011

The prediction of the long‐term behaviour of polymeric materials ageing outdoors can be based on the so‐called “mechanistic” approach, i.e. the recognition of the mechanisms of the chemical evolution in artificial photoageing and in weathering. As far as no physical ageing is involved, the variations through weathering of the physical properties are only due to the chemical evolution. In such conditions, the expansion scale for experiment time can be based on the acceleration of the ongoing chemistry in artificial photoageing.

To recognize the mechanisms previously observed in laboratory conditions, it is of main importance to identify the intermediate and final photoproducts in the first layers of the polymeric materials exposed outdoors. This detailed analysis can be carried out, at present time, by means of micro‐FTIR‐spectrophotometry, a recent development of FTIR spectroscopy, which allows measurements on 5–10 μm layers. Examples of determinations on polyamides, PVC and dienic elastomers will be presented and the origin of various photoproduct profiles will be discussed.
Thermolysis of diaryl disulfides: A new route to poly(arylene sulfide)s
Authors: Wang Zhi Yuan , Hay Allan S.
Published: March 2011

Thermolysis of diphenyl disulfide in the presence of iodoarenes yielded the corresponding unsymmetric diaryl sulfides. This new reaction has been utilized for the synthesis of high molecular weight poly(phenylene sulfide) and poly(naphthylene sulfide)s, starting from bis(4‐iodophenyl) disulfide and bis(iodonaphthyl) disulfides. Poly(phenylene sulfide) with a melting temperature above 250 °C was also obtained from bis(4‐bromophenyl) disulfide in the presence of a suitable reducing agent (e.g. potassium iodide). Heating bis(4‐chlorophenyl) disulfide afforded only a low molecular weight polymer. Bis(4‐fluorophenyl) disulfide remained stable under the same thermolysis conditions.
New synthesis of polyamides and related condensation polymers by using N‐trimethylsilyl‐substituted diamine monomers
Authors: Inai Yoshio
Published: March 2011

This article reviews our current work on the synthesis using N‐trimethylsilyl‐substituted diamines for polyamides and related condensation polymers. The polycondensations of N‐silylated aromatic diamines with aromatic dicarboxylic acid chlorides proceeded much more rapidly and yielded higher molecular weight aramids, compared with the polymerizations using the parent diamines. Thus, this method is efficient and versatile over the conventional diamine route for the synthesis of aramids, as well as other diamine‐based condensation polymers including polybenzoxazoles and polyimides having high molecular weights.
Polyrotaxanes: Synthetic methodologies & characterization
Authors: Gibson Harry W. , Engen Paul T. , Shen Xi Ya , Sze Jean , Lim Christina , Bheda Mukesh , Wu Charles
Published: March 2011

The synthesis of polyrotaxanes, comprised of linear macromolecules threaded through cyclic species, may be accomplished by either of two strategies: (1) statistical threading, in which the macrocycle is used as solvent and threading is predominantly entropically driven, or (2) template threading, involving an enthalpic driving force such as charge transfer or metal complexation. This paper summarizes our efforts in this field by describing syntheses by both step and chain growth methodologies and the characterization of the resultant polyrotaxanes. Examples include polyesters, polyethers, polyurethanes, polystyrene and polyacrylonitrile. The polyrotaxanes possess properties (thermal, solubility, mechanical, etc.) that differ from the corresponding linear polymers. In some systems phase separation occurs, producing morphologies that consist of crystalline macrocycles and either amorphous or crystalline linear backbones; these results demonstrate the ability of the macrocycles to move along the linear backbone in the melt without dethreading.
Benzocyclobutenes in polymer synthesis
Authors: Kirchhoff R. A. , Bruza K. , Carriere C. , Rondan N.
Published: March 2011

Benzocyclobutenes constitute the basis of a new and versatile approach to the synthesis of high performance polymers for applications in the electronics and aerospace industries. The basic technology involves a family of thermally polymerizable monomers which contains one or more benzocyclobutene groups per molecule. The benzocyclobutene when heated to 200°C undergoes a retrocyclic opening of the aliphatic four membered ring to afford the highly reactive o‐xylylene, which can either react with itself, or react with other sites of unsaturation leading to the formation of thermally stable polymers. Depending upon their functionality, these monomers can be polymerized to yield either thermoset or thermoplastic materials. The polymers typically exhibit good thermal stability and retention of mechanical properties at elevated temperature. The monomers are processable from the melt and are useful in the preparation of high temperature coatings, advanced composites and adhesives.
Interfacial interactions in particulate filled thermoplastics: Mechanism, strength, properties
Authors: Pukánszky Béla
Published: March 2011

Using the results of stress analysis the factors influencing the micromechanical deformations in particulate filled composites were studied. It was shown that interfacial interactions influence slightly shear yielding and crazing, but have a significant effect on dewetting. Interactions can be modified by surface treatment. Types and mechanisms of surface treatment are discussed. A model describing the composition dependence of tensile properties makes possible the quantitative evaluation of interaction. Attention is called to the importance of composite structure; aggregation, orientation of anisotropic particles, nucleating effect of the filler, all can change the properties of the composite.
Monosized polymer particles in biochemical and biomedical separations
Authors: Ellingsen Turid , Aune Oddvar , Berge Arvid , Kilaas Lars , Schmid Ruth , Stenstad Per , Ugelstad John , Hagen Steinar , Weng Ellen , Johansen Liv
Published: March 2011

The method of activated swelling allows production of highly monodisperse polymer particles in the range of 1 to 100μm, with identical bead‐to‐bead morphology. Monosized particles with a wide variety in content of crosslinker, pore size and pore size distribution have been evaluated in different areas of biotechnology. Underivatized macroporous particles have been developed for reversed phase and size exclusion chromatography in organic solvents. Supports for aqueous phase ion exchange have been produced by covalent coupling of a hydrophilic layer to the particle surface. These media give excellent characteristics with regard to selectivity, capacity and recoveries of biomolecules. In this paper proteins and peptides are used to illustrate chromatographic performance. Monosized polymer particles have been magnetized by a process where magnetic iron oxides are formed inside preformed monodisperse particles. These particles are used extensively in selective isolation of cells and bacteria and in DNA technology. This paper reviews some new results in the field of cell separation.
Use of micro‐FTIR spectrophotometry in the determination of polymer photoageing mechanisms
Authors: Lemaire Jacques , Gardette Jean‐Luc , Lacoste Jacques
Published: March 2011

The mechanisms of artificial accelerated photoageing, in the meaning of the “mechanistic” approach recently developed, have been determined for many classes of polymeric materials. The mechanism accounts for the formation and conversion of the main intermediate photoproducts and for the accumulation of final photoproducts. Based on the observed kinetics of the chemical evolution, described through the variations of a single critical photoproduct in artificial conditions and in the early stages of weathering, the lifetimes of polymeric materials can be predicted in many circumstances. Moreover, in the mechanistic approach, the influence of each photostabilizer (anti‐UV, conventional antioxidant, redox antioxidant, hydroperoxide reducer) is evaluated and rationalized from the rate of formation of the critical photoproducts. The recognition of the on‐going mechanism which controls the weathering of unstabilized and stabilized polymers is therefore of major importance to allow the conversion of data collected in laboratory to data corresponding to the real use. Fourier Transform Infrared (FTIR) microspectrophotometric determinations of profiles of final critical photoproducts and of residual photostabilizers afford a direct control of the relevancy of laboratory experiments. This recent technique which couples the FTIR technique and IR microscopy allows a full chemical analysis of 100 μm2‐microzones or of 5 μm‐elementary layers at the surface of the sample. Profiles could be determined up to 200–300 μm from the surface. Examples of polymers whose photoageing is completely controlled by chemical defects like pigmented poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) will be presented. Photooxidation, thermooxidation and ozonization of dienic elastomers will be compared to actual weathering to demonstrate the irrelevancy of the ozone test for the prediction of longterm behaviour of elastomers in the presence of light.
Comparison of living polymerization systems
Authors: Iván Béla
Published: March 2011

Recent developments in the field of living polymerization are surveyed. Comparison of the available mechanistic and kinetic information is made for living anionic, cationic, free radical, group transfer, ring‐opening metathesis, Ziegler‐Natta and immortal polymerizations. This evaluation indicates that the majority of living polymerizations involve quasiliving equilibrium between active (propagating) and dormant (nonpropagating) polymer chains. On the basis of the kinetics of a general model for quasiliving and ideal living polymerizations it is concluded that ideal living polymerization is a special subclass of quasiliving polymerizations. Classification of living polymerization systems is also attempted.
Polymer chains in good solvent within attracting walls
Authors: Allegra G.
Published: March 2011

It is known that a polymer chain in an ideal solvent confined within parallel attracting walls undergoes a second‐order transition at the temperature T* satisfying the equation exp[‐ε/(kBT*)]=6/5; here the model consists of a chain placed on a cubic lattice, and ε (<0) is the attractive energy experienced by a chain segment contacting a wall.

We then investigate the effect induced by a good solvent upon the chain behavior. A single chain is considered; within the Gaussian approximation, we assume that its partition function may be factorized in two terms, one across the wall planes and another parallel to them. For an interplanar distance L significantly smaller than the average radius of gyration the compressed chain is assumed to reach a uniform density, so that the free energy contribution due to the intrachain atomic contacts is a function of the density alone. It may be shown that the effective value of ε/(kBT*)(=σ) is the difference between the value to be expected “in vacuo” and β/(z‐2), where z is the degree of coordination of the lattice and β is the excluded‐volume parameter. As a result, for large values of L we may have an attractive effect exerted by the chain on the walls whereas at small L's we invariably have a repulsion. For the cubic lattice we have a repulsion and an attraction for large L approximatively for σ < ln(6/5)+β/(z‐2) and for σ > (ln(6/5)+β/(z‐2), respectively, whereas we have inversion between the two regimes at some distance L for intermediate values of σ. In the limit of an infinite molecular weight the inversion translates into a thermodynamic transition.

We believe the present model may explain some important features seen in polymer adhesion.
Giulio Natta: The man and the scientist
Authors: Allegra G.
Published: March 2011

Giulio Natta was a man strongly involved from an emotional viewpoint in his research activity, and in that sort of reflections he was so absorbed as to give the impression that he was living in his own world. Nevertheless, in spite of the enormous amount of work he was carrying on virtually day and night through study, writing of his own papers and uninterrupted reflection, he was a man of a vast culture in Natural Sciences, especially Mineralogy and Botany. Besides, until allowed by his health, he loved to live in the open air and, especially, mountain excursions. He could manifest much sympathy and personal involvement to the people close to him, as I may witness myself for the thirteen years I was one of his coworkers. On the whole, in spite of his absorbed and somewhat shy appearance, he was a man who deeply loved life.
Polymer research directions to meet the needs of the 21st century
Authors: Meyer James M.
Published: March 2011

The polymer industry in the world has grown from about 15 million pounds in 1923 to over 60 billion pounds in 1990 representing a compound annual growth rate of 15% for nearly 70 years. This dynamic behavior will continue in the 21st century. However, the growth will be faster in the developing nations than inthe developed nations. The basis for this projection of continued growth is provided by looking at the estimated per capita consumption of polymers for different regions of the world shown in Figure 1.
Evolution of the structure of mesophase polyfluoroalk‐oxyphosphazenes and liquid crystalline copolyesters
Authors: Plate' Nikolai A. , Antipov Evgenij M.
Published: March 2011

Comparative analysis of the temperature evolution of the structure of linear organoelement polyfluoroalkoxyphosphazenes and wholly aromatic main‐chain copolyesters was carried out using X‐ray analysis, differential scanning calorimetry and dynamic mechanical testing within a wide temperature range. Experimental observations show that flexible‐chain polyfluoroalkoxyphosphazenes are inclined to formation of the columnar mesophase and condis crystalline structures, while rigid‐chain random copolyesters mainly exhibit peculiar smectic and nematic liquid crystalline states.