bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathways from infant exposure to marital conflict to parent–toddler role reversal
Authors: Macfie Jenny , Houts Renate M. , Pressel Abigail S. , Cox Martha J.
Published: July 2008

We know that exposure to marital conflict places infants at risk, but we know less about processes. One process may be role reversal, when a distressed parent looks to the child to meet unmet needs for comfort, intimacy, or companionship. A parent in marital conflict may be particularly prone to role reversal, which in turn adversely affects child development. The current study examined pathways from infants' exposure to marital conflict at 12 months to role reversal at 24 months. We sampled low–middle socioeconomic status (SES) families with their first child (N = 128). Independent observers assessed marital conflict (in a problem‐solving task) and role reversal (in a story‐telling task). We found that each parent's conflict behavior predicted the other parent's role reversal. In a direct pathway, mother's conflict behavior towards father led directly to father's role reversal with the child. In an indirect pathway, father's conflict behavior towards mother led to his withdrawal from her, which in turn led to mother's role reversal with the child. Clinical implications are discussed within a developmental psychopathology framework in terms of preventive interventions to offset the deleterious effect of marital conflict and role reversal on child development.
The Chances for Children Teen Parent–Infant Project: Results of a pilot intervention for teen mothers and their infants in inner city high schools
Authors: Mayers Hillary A. , Hager‐Budny Michaela , Buckner Elizabeth B.
Published: July 2008

Adolescent motherhood poses serious challenges to mothers, to infants, and ultimately to society, particularly if the teen mother is part of a minority population living in an urban environment. This study examines the effects of a treatment intervention targeting low‐income, high‐risk teen mothers and their infants in the context of public high schools where daycare is available onsite. Our findings confirm the initial hypothesis that mothers who received intervention would improve their interactions with their infants in the areas of responsiveness, affective availability, and directiveness. In addition, infants in the treatment group were found to increase their interest in mother, respond more positively to physical contact, and improve their general emotional tone, which the comparison infants did not. Importantly, these findings remain even within the subset of mothers who scored above the clinical cutoff for depression on the Center for Epidemiological Studies‐Depression Scale (CES‐D; L. Radloff, 1977), confirming that it is possible to improve mother–infant interaction without altering the mother's underlying depression. The implications of these findings are significant both because it is more difficult and requires more time to alter maternal depression than maternal behavior and because maternal depression has been found to have such devastating effects on infants.
Violated wishes about division of childcare labor predict early coparenting process during stressful and nonstressful family evaluations
Authors: Khazan Inna , McHale James P. , Decourcey Wendy
Published: July 2008

Prior research has indicated that expectant parents overestimate the extent to which fathers will take part in the “work” of parenting, with mothers often becoming disenchanted when these expectations are violated following the baby's arrival. In this study, we examine the role of violated wishes concerning childcare involvement in accounting for variability in maternal and paternal marital satisfaction, and in early coparenting behavior as assessed during family‐interaction sessions. The results indicate possible negative effects of violated wishes on the enacted family process and confirm previous findings regarding the effects of marital satisfaction. In addition, we uncovered differences in the way that violated maternal wishes are related to coparenting during playful and mildly stressful family interactions.
Membrane transport enhancement of chlorin e6‐polyvinylpyrrolidone and its photodynamic efficacy on the chick chorioallantoic model
Authors: Chin William Wei Lim , Heng Paul Wan Sia , Lim Pei Li , Lau Weber Kam On , Olivo Malini
Published: July 2008

We have determined the influences of polyvinylpyrrolidone (PVP) on the topical delivery of chlorin e6 (Ce6) in malignant bladder cells. The chick chorioallantoic membrane (CAM) was used to model the tumor spheroids that resemble small residual bladder tumors prior to vascularization. Macroscopic fluorescence imaging showed that Ce6‐PVP‐induced fluorescence had a higher sensitivity and specificity for delineating tumor from the adjacent normal CAM compared to Ce6 alone. Nonlinear regression analyses have shown that Ce6‐PVP has a longer half‐life in the tumor compared to Ce6. The uptake ratio of Ce6‐PVP was found to have a 2‐fold increase across the CAM when compared to that of Ce6, indicating that PVP was able to facilitate diffusion of Ce6 across the membrane. Confocal laser scanning microscopy further confirmed that Ce6‐PVP has better penetration in the CAM as well as in the tumor cells compared to Ce6. The present work contributes to our understanding of the Ce6‐PVP drug–polymer system by demonstrating for the first time that the presence of PVP facilitates the transport of Ce6 across the chorioallantoic membrane. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural stability of green fluorescent proteins entrapped in polyelectrolyte nanocapsules
Authors: Krol Silke , Cannone Fabio , Caccia Michele , Sironi Laura , Bianchini Paolo , Campanini Barbara , Collini Maddalena , Chirico Giuseppe , Diaspro Alberto
Published: July 2008

Molecules of a green fluorescent protein mutant, GFPmut2, have been immobilized in nanocapsules, assemblies of charged polyelectrolyte multilayers, with the aim to study the effect of protein‐polyelectrolyte interactions on the protein stability against chemical denaturation. GFPmut2 proteins turn out to be stabilized and protected against the denaturating action of small chemical compounds. The nanocapsule protective effect on GFPmut2 is likely due to protein interactions with the negatively charged polymers, that induce an increase in the local rigidity of the protein nano‐environment. This suggestion is supported by Fluorescence Polarization measurements on GFPmut2 proteins bound to the NC layers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Postpartum plasma exchange as adjunctive therapy for severe acute fatty liver of pregnancy
Authors: Martin James N. , Briery Christian M. , Rose Carl H. , Owens Michelle T. , Bofill James A. , Files Joe C.
Published: July 2008

Acute fatty liver of pregnancy (AFLP) is a rare disease of progressive hepatic insufficiency and secondary systemic compromise that poses significant fetal‐maternal risk. Plasma exchange (PEX) is an effective bridge therapy to sustain liver function and enable hepatocellular regeneration to occur in nonpregnant patients following acute decompensation of a chronic liver disease or while awaiting liver transplantation. The application of PEX for patients with AFLP is a novel concept; since 1988 we have utilized postpartum PEX (PPEX) as adjunctive medical therapy for six patients with severe AFLP. Before PPEX initiation, four patients had signs and symptoms of encephalopathy, three required ventilatory support, five had advanced liver insufficiency, and all six were developing renal failure. PPEX was initiated 2–8 days following delivery and repeated (two to four times, mean = 3) at 24–48‐h intervals thereafter. All patients responded with composite clinical (symptoms/signs) and laboratory improvement; the average length of hospitalization following final PPEX for five of six patients was 7 days. No significant PPEX‐related complications occurred. PPEX utilization in patients with severe AFLP may enhance maternal recovery by preventing secondary sequelae from hepatic insufficiency until spontaneous healing can occur. Further study appears to be indicated to validate a role for PPEX as supportive therapy for puerperal patients with AFLP suffering multiorgan failure. J. Clin. Apheresis, 2008. © 2008 Wiley‐Liss, Inc.
The impact of colony‐stimulating factor‐1 on fracture healing: An experimental study
Authors: Sarahrudi Kambiz , Mousavi Mehdi , Grossschmidt Karl , Sela Nezir , König Franz , Vécsei Vilmos , Aharinejad Seyedhossein
Published: July 2008

The role of colony stimulating factor‐1 (CSF‐1) in the regulation of osteoclasts and bone remodeling suggests that CSF‐1 may also be involved in regulation of bone healing. The ability of CSF‐1 to promote healing of bone defects was tested in a rabbit model. Twenty‐four New Zeeland rabbits were included in the study. Animals were assigned to two groups: the control group (n = 12) was treated by plate fixation. The animals in the second group (n = 12) were also stabilized by conventional plating and received additionally CSF‐1 for 2 weeks systemically. Histologic, histomorphometric, and radiologic examinations were performed to evaluate the healing process at 4, 8, and 12 weeks following surgery. Animals that were treated by CSF‐1 produced a significantly higher amount of mineralized bone over the first 8 weeks after fracture compared to the control animals. Furthermore, a higher number of osteoclasts was found in CSF‐1‐treated animals within the first 8 weeks, compared to the controls. The present data emphasize for the first time the importance of CSF‐1 in the bone healing. The use of CSF‐1 in addition to conventional fixation might be a novel approach for the treatment of bone defects. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:36–41, 2009
Autologous nucleus pulposus primes T cells to develop into interleukin‐4‐producing effector cells: An experimental study on the autoimmune properties of nucleus pulposus
Authors: Geiss Andrea , Larsson Karin , Junevik Katarina , Rydevik Björn , Olmarker Kjell
Published: July 2008

An autoimmune response to herniated nucleus pulposus has been proposed to constitute a pathophysiologic mechanism for inducing sciatica based on the fact that nucleus pulposus under normal conditions is excluded from the development of immunological tolerance. The manifestation of an autoimmune response comprises different steps starting with antigen capture, continuing with activation of T helper (TH) cells and ending with production of autoantibodies. Activated TH cells differentiate into either TH1 cells, predominately producing proinflammatory cytokines such as interferon γ (IFNγ) or a TH2 subset mainly producing anti‐inflammatory cytokines such as interleukin‐4 (IL‐4). The aim of the present study was to examine if exposure of autologous nucleus pulposus (NP) to the immune system for 3 weeks is potent enough to prime TH cells to differentiate into TH2 cells. The study was performed in a pig model allowing the exposure of NP to the immune system. To assess the polarization of TH cells the intracellular production of IFNγ and IL‐4 was measured in T cells by using flow cytometry. The revealed predominant production of IL‐4 together with low production of IFNγ in T cells after NP exposure to the immune system indicates that nucleus pulposus may prime TH cells to develop into IL‐4‐producing TH2 cells after being exposed to the immune system, for example, in association with disc herniation. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:97–103, 2009
Protective effects of preconditioned local somatothermal stimulation on neuromuscular plasticity against ischemia–reperfusion injury in rats
Authors: Pan Po‐Jung , Chan Rai‐Chi , Yang An‐Hang , Chou Chen‐Liang , Cheng Ya‐Fang , Chiu Jen‐Hwey
Published: July 2008

The aim of this study was to investigate whether preconditioned local somatotheral stimulation (LSTS) protects the muscle and nerve against ischemia–reperfusion (I/R) injuries. Male rats were randomly assigned to normal, preconditioned LSTS only, and I/R‐injured groups with or without LSTS preconditioning. I/R injuries of the lower limb were induced by rubber band wrapping, followed by measurements of gait function and nerve conduction, muscle pathology, serum enzymatic activity, and the expression of heat‐shock protein 70 (HSP‐70) in the gastrocnemius muscles. No significant change of neuromuscular function was found between LSTS (−) and LSTS (+) groups on the first day after I/R injury. In contrast, gait stride length, compound motor action potential, and serum creatine phosphokinase MM isoenzyme were significantly improved on the eighth day after one or two doses of preconditioned LSTS and subsequent I/R injury. Western blot analysis disclosed no significant change of HSP‐70 expression in the muscle of I/R injured limbs between LSTS (−) and LSTS (+) groups. We conclude that preconditioned LSTS is a safe modality that improves the neuromuscular plasticity against I/R injured limbs, which provides a new strategy for I/R injury in clinical applications, such as intraoperative use of tourniquets. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Serum ion levels after ceramic‐on‐ceramic and metal‐on‐metal total hip arthroplasty: 8‐year minimum follow‐up
Authors: Savarino Lucia , Padovani Giovanni , Ferretti Massimo , Greco Michelina , Cenni Elisabetta , Perrone Giorgio , Greco Francesco , Baldini Nicola , Giunti Armando
Published: July 2008

Alternative bearing surfaces for total hip arthroplasty, such as metal‐on‐metal and ceramic‐on‐ceramic, offer the potential to reduce mechanical wear and osteolysis. In the short and medium term, the second generation of metal‐on‐metal bearings demonstrated high systemic metal ion levels, whereas ceramic‐on‐ceramic bearings showed the lowest ones. We aimed to verify whether the long‐term ion release in metal‐on‐metal subjects was still relevant at a median 10‐year follow‐up, and whether a fretting process at the modular junctions occurred in ceramic‐on‐ceramic patients and induced an ion dissemination. Serum levels were measured in 32 patients with alumina‐on‐alumina implants (group A), in 16 subjects with metal‐on‐metal implants (group B), and in 47 healthy subjects (group C). Group B results were compared with medium‐term findings. Cobalt and chromium levels were significantly higher in metal‐on‐metal implants than in ceramic‐on‐ceramic ones and controls. Nevertheless, ion levels showed a tendency to decrease in comparison with medium‐term content. In ceramic‐on‐ceramic implants, ion values were not significantly different from controls. Both in groups A and B, aluminum and titanium release were not significantly different from controls. In conclusion, negligible serum metal ion content was revealed in ceramic‐on‐ceramic patients. On the contrary, due to the higher ion release, metal‐on‐metal coupling must be prudently considered, especially in young patients, in order to obtain definitive conclusions. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Controlled release of GDNF reduces nerve root‐mediated behavioral hypersensitivity
Authors: Hubbard Raymond D. , Martínez Joan J. , Burdick Jason A. , Winkelstein Beth A.
Published: July 2008

Nerve root compression produces persistent behavioral sensitivity in models of painful neck injury. This study utilized degradable poly(ethylene glycol) hydrogels to deliver glial cell line‐derived neurotrophic factor (GDNF) to an injured nerve root. Hydrogels delivered ∼98% of encapsulated GDNF over 7 days in an in vitro release assay without the presence of neurons and produced enhanced outgrowth of processes in cortical neural cell primary cultures. The efficacy of a GDNF hydrogel placed on the root immediately after injury was assessed in a rat pain model of C7 dorsal root compression. Control groups included painful injury followed by: (1) vehicle hydrogel treatment (no GDNF), (2) a bolus injection of GDNF, or (3) no treatment. After injury, mechanical allodynia (n = 6/group) was significantly decreased with GDNF delivered by the hydrogel compared to the three injury control groups (p < 0.03). The bolus GDNF treatment did not reduce allodynia at any time point. The GDNF receptor (GFRα‐1) decreased in small, nociceptive neurons of the affected dorsal root ganglion, suggesting a decrease in receptor expression following injury. GDNF receptor immunoreactivity was significantly greater in these neurons following GDNF hydrogel treatment relative to GDNF bolus treated and untreated rats (p < 0.05). These data suggest efficacy for degradable hydrogel delivery of GDNF and support this treatment approach for nerve root‐mediated pain. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:120–127, 2009
Three‐state model for femtosecond broadband stimulated Raman scattering
Authors: Sun Z. , Qiu Xue Q. , Lu J. , Zhang Dong H. , Lee Soo‐Y.
Published: July 2008

Stimulated Raman scattering (SRS) is analyzed with a three‐state model. Using a diagrammatic density‐matrix formalism, SRS by a pair of Raman pump and probe pulses, with observation along the probe direction, is described principally by eight terms. The eight terms can be grouped into four sets, which are labeled as SRS or IRS (inverse Raman scattering): SRS(I), SRS(II), IRS(I), and IRS(II). Specializing to the case of femtosecond SRS (FSRS) by a picosecond (ps) Raman pump pulse and a femtosecond (fs) probe pulse, the spectra for the four sets of terms under off‐resonance and resonance conditions were calculated. The results obtained can explain the FSRS experimental observations from a (decaying) stationary vibrational state, such as (1) high wavenumber resolution (determined by the narrow bandwidth Raman pump pulse) and high time resolution (determined by the fs probe pulse), (2) Stokes gain vs anti‐Stokes loss in off‐resonance FSRS, and (3) dispersive lineshapes in resonance FSRS. Copyright © 2008 John Wiley & Sons, Ltd.
Solvent effects on the spectrokinetic studies on the molecular complexes of dextromethorphan and atenolol drugs with DDQ
Authors: Pandeeswaran M. , Elango K. P.
Published: July 2008

The kinetics and mechanism of the interaction between 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) and dextromethorphan and atenolol drugs has been investigated spectroscopically. In the presence of large excess of donor drug, the 1:1 charge transfer (CT) complex is transformed into a final product, which has been isolated and characterized by using FT‐IR and GC‐MS techniques. The rate of formation of product has been measured as a function of time in different solvents at three temperatures. The thermodynamic parameters, viz. activation energy, enthalpy, entropy, and free energy of activation were computed from temperature dependence of rate constants. On the basis of the spectrokinetic results, a plausible mechanism for the formation of the CT complex and its transformation into final product is presented and discussed. Cyclic voltammetric study supports the observed solvent effect on the extent of CT complexation and the rate with which it is converted into the product. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 559–568, 2008
The role of symplectic integrators in optimal control
Authors: Chyba Monique , Hairer Ernst , Vilmart Gilles
Published: July 2008

For general optimal control problems, Pontryagin's maximum principle gives necessary optimality conditions, which are in the form of a Hamiltonian differential equation. For its numerical integration, symplectic methods are a natural choice. This article investigates to which extent the excellent performance of symplectic integrators for long‐time integrations in astronomy and molecular dynamics carries over to problems in optimal control.

Numerical experiments supported by a backward error analysis show that for problems in low dimension close to a critical value of the Hamiltonian, symplectic integrators have a clear advantage. This is illustrated using the Martinet case in sub‐Riemannian geometry. For problems like the orbital transfer of a spacecraft or the control of a submerged rigid body, such an advantage cannot be observed. The Hamiltonian system is a boundary value problem and the time interval is in general not large enough so that symplectic integrators could benefit from their structure preservation of the flow. Copyright © 2008 John Wiley & Sons, Ltd.
The use of pharmacological treatments for people with personality disorder: A systematic review of randomized controlled trials
Authors: Duggan Conor , Huband Nick , Smailagic Nadja , Ferriter Michael , Adams Clive
Published: July 2008

Background This is a companion paper to our earlier review of psychological treatments for people with personality disorder that examined the evidence from randomized controlled trials (RCTs). Here, we report on the evidence of pharmacological treatments from RCTs for people with personality disorder. As in the previous report, this paper incorporates information from an earlier review that examined the evidence to 2002, and extends it to December 2006. As in the previous paper, this review restricts itself to the findings from RCTs, and excludes evidence from other study designs; however, details of these other studies will be posted in the National Personality Disorder Institute Website (http://www.pdinstitute.org.uk).

Aim This study aimed to examine the evidence from RCTs to justify intervening with pharmacological treatments in people with personality disorder.

Method Fifteen electronic databases (including MEDLINE, EMBASE and PsycINFO) were searched to the end of December 2006 for any RCT of a pharmacological intervention for participants meeting DSM or ICD criteria for personality disorder. Outcomes were grouped using a similar symptomological categorization to that suggested by Soloff in 1998.

Results This methodology identified 35 trials for inclusion. The main positive findings were those favouring the use of anticonvulsants to reduce aggression, and of anti‐psychotics to reduce cognitive perceptual and mental state disturbance. However, there were major methodological deficiencies in the trial designs, including small numbers of participants and limited duration of treatment and follow‐up.

Conclusion This review identifies a very limited evidence base to justify intervening with drugs in this group. Reasons why this should be so are examined that relate to fundamentally differing conceptualizations of how any intervention might impact in an individual with personality disorder. Copyright © 2008 John Wiley & Sons, Ltd.
The NHS forensic mental health R&D programme: Developing new talent or maintaining a stage army?
Authors: Soothill Keith , Harney Kathryn , Maggs Adele , Chilvers Clair
Published: July 2008

This paper considers the successful recipients of the 79 project awards made during the 12‐year ‘life’ (1996–2007) of the NHS Forensic Mental Health (FMH) R&D programme. The focus is on whether the 213 persons (principal investigators (PIs) and/or co‐investigators (CIs)) represent new talent or existing academic entrepreneurs in the FMH field. Amongst PIs, awards were almost without exception given to researchers with an established research track record. Forensic psychiatrists continue to be the main players, but other research groupings are emerging as PIs. In contrast, CIs range more widely in terms of previous research experience and professional background. 38.5 percent had no apparent experience of previous funded research projects apart from grants funded by the FMH programme. Hence, CIs are the source of new talent amongst the programme's project awards. The authors warn of the dangers of losing the benefits of this investment as policy priorities shift. Copyright © 2008 John Wiley & Sons, Ltd.
Kinetics of ethylene polymerization reactions with chromium oxide catalysts
Authors: Kissin Yury V. , Brandolini Anita J. , Garlick Joyce L.
Published: July 2008

Principal kinetic data are presented for ethylene homopolymerization and ethylene/1‐hexene copolymerization reactions with two types of chromium oxide catalyst. The reaction rate of the homopolymerization reaction is first order with respect to ethylene concentration (both for gas‐phase and slurry reactions); its effective activation energy is 10.2 kcal/mol (42.8 kJ/mol). The r1 value for ethylene/1‐hexene copolymerization reactions with the catalysts is ∼30, which places these catalysts in terms of efficiency of α‐olefin copolymerization with ethylene between metallocene catalysts (r1 ∼ 20) and Ti‐based Ziegler‐Natta catalysts (r1 in the 80–120 range). GPC, DSC, and Crystaf data for ethylene/1‐hexene copolymers of different compositions produced with the catalysts show that the reaction products have broad molecular weight and compositional distributions. A combination of kinetic data and structural data for the copolymers provided detailed information about the frequency of chain transfer reactions for several types of active centers present in the catalysts, their copolymerization efficiency, and stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5315–5329, 2008
Hybrid linear dendritic macromolecules: From synthesis to applications
Authors: Gitsov Ivan
Published: July 2008

Linear‐dendritic copolymers are intriguing macromolecules, which offer challenge and fascination as purely synthetic objects at the crossroad of organic and polymer chemistry and as promising materials for diverse advanced applications. This review traces their discovery and highlights the synthetic strategies used for their construction. The ambivalent character of the linear‐dendritic architecture opens numerous avenues towards emerging and potential applications. Specific solution properties enable the construction of nanometer‐sized nanoreactors for reactions in environmentally friendly media, and the creation of “nanosponges” for selective passive binding of fluorescent pH‐indicators for environmental or biomonitoring. Another structure–property relationship is used for noncovalent and site‐specific modification of glycoproteins, which leads to the formation of “semiartificial” enzymes with enhanced and broadened catalytic activity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5295–5314, 2008
A novel and versatile potassium‐based catalyst for the ring opening polymerization of cyclic esters
Authors: Lemmouchi Yahia , Perry Michael C. , Amass Allan J. , Chakraborty Khirud , Schacht Etienne
Published: July 2008

Poly(lactide) (PLA), poly(ε‐caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) homopolymers of high molecular weight were prepared using potassium‐based catalyst. Polymerizations were carried out in toluene at room temperature. The chemical structure of the polymers was investigated by 1H and 13C NMR. The physical properties investigated by GPC and DSC for the polymers obtained are similar to those prepared using tin octanoate based catalyst. Using a sequential polymerization procedure, PLA‐b‐PCL, PLA‐b‐PTMC, and PCL‐b‐PTMC diblock copolymers were synthesized and characterized in terms of their composition and physical properties. The formation of diblock copolymers was confirmed by NMR and DSC measurements. In vitro cytotoxicity tests have been carried out using MTS assay and the results show the biocompatibility of these polymers in the presence of the fibroblast cells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5348–5362, 2008
Syntheses and alignment behavior of liquid crystalline polymethacrylates having 2‐ and 4‐styrylpyridine moieties
Authors: Kwak Giseop , Kim Min‐Woo , Park Deok‐Ha , Kong Jong‐Yun , Hyun Seok‐Hee , Kim Woo‐Sik
Published: July 2008

Two kinds of polymethacrylates, 1 and 2, with 2‐styrylpyridine and 4‐styrylpyridine moiety as a photoreactive group, which have a benzoate group as a mesogenic unit, and hexylene group as a flexible spacer in the same side chain, were synthesized to characterize their alignment behaviors. The UV absorption and fluorescence studies on the two polymers revealed that the latter polymer with the 4‐stylrylpyridine moiety is more aggregative than the former polymer with the 2‐styrylpyridine moiety. The polymer 1 showed a nematic phase structure at 170 °C, while 2 appeared in a partially bilayered smectic A phase structure in the homeotropic direction at 175 °C. The polymer 1 film generated an in‐plane alignment by a linearly polarized UV light irradiation and subsequent annealing, and its direction was parallel with respect to the irradiation. On the other hand, the polymer 2 film with the same treatments gave a high out‐of‐plane order parameter of 0.73 in a wide temperature range of 120–240 °C. The significant differences in the aggregation behavior, the liquid‐crystalline structure, and the alignment between the two polymers were discussed by the structural differences between the 2‐ and 4‐styrylpyridine moieties in the two polymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5371–5380, 2008
In situ polymerization of ethylene using metallocene catalysts: Effect of clay pretreatment on the properties of highly filled polyethylene nanocomposites
Authors: Leone Giuseppe , Bertini Fabio , Canetti Maurizio , Boggioni Laura , Stagnaro Paola , Tritto Incoronata
Published: July 2008

Highly filled polyethylene (PE)‐based nanocomposites were obtained by insitu polymerization technique. An organically modified montmorillonite, Cloisite® 15A (C15A), was previously treated with methylaluminoxane (MAO) to form a supported cocatalyst (C15A/MAO) before being contacted with a zirconocene catalyst. The main features of C15A/MAO intermediates were studied by elemental analysis, TGA, TGA‐FTIR, WAXD, and TEM. MAO reacts with the clay, replaces most of the organic surfactant within the clay galleries and destroys the typical crystrallographic order of the nanoclay. The catalytic activity in the presence of C15A/MAO is higher than in ethylene polymerization without any inorganic filler and increases with MAO supportation time. This indicates that part of the polymer chains grows within the clay galleries, separates them, and makes it possible to tune the final morphology of the composites. The polymerization results and the influence of C15A pretreatment and polymerization conditions on thermal and morphological properties of the hybrid PE/C15A nanocomposites are presented. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5390–5403, 2008
Synthesis and characterization of a novel mid‐chain macrophotoinitiator of polyacrylonitrile by Ce(IV)/HNO3 redox system
Authors: Degirmenci Mustafa , Taskesen Edip , Hicri Sirin , Yilmaz Hasim
Published: July 2008

The polymerization of acrylonitrile initiated by cerium(IV) ammonium nitrate in combination with dihydroxy functional photoinitiator namely, 2‐hydroxy‐1‐[4‐(2‐hydroxyethoxy)phenyl]‐2‐methyl propan‐1‐one (HE‐HMPP), Irgacure 2959, has been investigated in aqueous nitric acid. A novel mid‐chain macrophotoinitiator of polyacrylonitrile (PAN) was obtained. The effects of acrylamide (AAm), HE‐HMPP, Ce(IV), and HNO3 concentrations and temperature on the polymerization rate, monomer conversion, and intrinsic viscosities were investigated. The photodegradation and IR, H NMR, UV, and fluorescence spectroscopic studies revealed that PAN with desired photoinitiator functionality in the middle of the chain was obtained. The obtained PAN was used as prepolymer for photoinduced free radical polymerization of methyl methacrylate (MMA) and AAm to produce block copolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5404–5413, 2008
Synthesis and characterization of well‐defined block and statistical copolymers based on lauryl methacrylate and 2‐(acetoacetoxy)ethyl methacrylate using RAFT‐controlled radical polymerization
Authors: Demetriou Maria , Krasia‐Christoforou Theodora
Published: July 2008

Four well‐defined diblock copolymers and one statistical copolymer based on lauryl methacrylate (LauMA) and 2‐(acetoacetoxy)ethyl methacrylate (AEMA) were prepared using reversible addition‐fragmentation chain transfer (RAFT) polymerization. The polymers were characterized in terms of molecular weights, polydispersity indices (ranging between 1.12 and 1.23) and compositions by size exclusion chromatography and 1H NMR spectroscopy, respectively. The preparation of the block copolymers was accomplished following a two‐step methodology: First, well‐defined LauMA homopolymers were prepared by RAFT using cumyl dithiobenzoate as the chain transfer agent (CTA). Kinetic studies revealed that the polymerization of LauMA followed first‐order kinetics demonstrating the “livingness” of the RAFT process. The pLauMAs were subsequently used as macro‐CTA for the polymerization of AEMA. The glass transition (Tg) and decomposition temperatures (ranging between 200 and 300 °C) of the copolymers were determined using differential scanning calorimetry and thermal gravimetric analysis, respectively. The Tgs of the LauMA homopolymers were found to be around −53 °C. Block copolymers exhibited two Tgs suggesting microphase separation in the bulk whereas the statistical copolymer presented a single Tg as expected. Furthermore, the micellization behavior of pLauMA‐b‐pAEMA block copolymers was investigated in n‐hexane, a selective solvent for the LauMA block, using dynamic light scattering. pLauMA‐b‐pAEMA block copolymers formed spherical micelles in dilute hexane solutions with hydrodynamic diameters ranging between 30 and 50 nm. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5442–5451, 2008
Detitanation of MgCl2‐supported Ziegler‐Natta catalysts for the study of active sites organization
Authors: Ribour David , Monteil Vincent , Spitz Roger
Published: July 2008

Thermal treatments under vacuum of conventional supported Ziegler‐Natta precatalysts (MgCl2/TiCl4/Dibutylphthalate) were conducted to gradually remove titanium to modify the active sites distribution. Only limited detitanations of precatalysts were achieved paying attention not to chemically alter the internal donor (T < 150 °C). Used in combination with the required cocatalyst and external donor in the propylene slurry polymerization, the modified precatalysts exhibited a drop of activity versus decreasing titanium content but the distributed polymer properties are almost not affected (a slight narrowing of molecular weight distribution was observed). After a titanium chloride secondary impregnation (possibly done in presence of an additional Lewis base), activity resumed but polymer properties are once again unchanged. These findings highlight the difficulty to separate the different families of active sites and lead us to propose a cluster organization of titanium active sites. Active sites are composed of titanium clusters having a size distribution at the precatalyst surface, possessing a critical operating size and operating collectively in polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5461–5470, 2008
Preparation of novel acrylamide‐based thermoresponsive polymer analogues and their application as thermoresponsive chromatographic matrices
Authors: Akiyama Yoshikatsu , Shinohara Yasurou , Hasegawa Yukio , Kikuchi Akihiko , Okano Teruo
Published: July 2008

New thermoresponsive polymers based on poly(N‐(N′‐alkylcarbamido)propyl methacrylamide) analogues were designed with increased hydrophobic content to facilitate temperature‐dependent chromatographic separations of peptides and proteins from aqueous mobile phases. These polymer solution exhibited a lower critical solution temperature (LCST) when the alkyl group is methyl, ethyl, isopropyl, propyl, butyl, and isobutyl. However, larger alkyl groups such as hexyl and phenyl were not soluble in aqueous solutions at any temperature. Phase transition temperatures were lower for larger alkyl groups and increased with decreasing polymer molecular weight and concentration in solution. LCST dependence on polymer molecular weight and concentration is more significant compared with well‐studied poly(N‐isopropylacrylamide) (PIPAAm). Partition coefficient (log P) values for N‐(N′‐butylcarbamide)propylmethacrylamide and N‐(N′‐isobutylcarbamide)propyl methacrylamide (iBuCPMA) monomers are larger than that for IPAAm monomer, suggesting higher hydrophobicity than IPAAm. Chromatographic evaluation of poly(N‐(N′‐isobutylcarbamide)propyl methacrylamide) (PiBuCPMA) grafted silica particles in aqueous separations revealed larger k′ values for peptides, insulin, insulin chain B, and angiotensin I than PIPAAm‐grafted silica beads. In particular, k′ values for insulin obtained from PiBuCPMA‐grafted silica separations were much larger than those from PIPAAm‐grafted surface separations, indicating that PiBuCPMA should be more hydrophobic than PIPAAm. These results support the introduction of alkylcarbamido groups to efficiently increase thermoresponsive polymer hydrophobicity of poly(N‐alkylacrylamides) and poly(N‐alkylmethacrylamides). Consequently, poly(N‐(N′‐alkylcarbamido)propyl methacrylamide) analogues such as PiBuCPMA and poly(N‐(N′‐alkylcarbamido)alkylmehacrylamide) are new thermoresponsive polymers with appropriate hydrophobic partitioning properties for protein and peptide separations in aqueous media, depending on selection of their alkyl groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5471–5482, 2008
Highly fluorescent mono‐substituted poly(arylacetylene)s containing tolane chromophores
Authors: Han Chien‐Chung , Balasubramanian Arumugam
Published: July 2008

A new class of highly fluorescent mono‐substituted polyarylacetylenes (P1–P3) has been successfully prepared with good yields and high molecular weights from a series of phenylethynylene‐substituted arylacetylenes (M1–M3), using W‐based catalyst. These polymers are readily soluble in common organic solvents (e.g., THF, toluene, and chloroform) and thermally stable up to ∼350 °C. Both 1H NMR and IR studies confirmed that all the monomers were selectively polymerized at the terminal triple bond. The 1H NMR results showed that both P1 and P2 have essentially trans‐polyene backbone structures, while P3 contains significant amounts of both cis‐ and trans‐structures. Coincidently, the photoluminescence (PL) intensity of P3 is also much lower than both P1 and P2. Nevertheless, the PL intensity of P1–P3 are all much higher than that of PPA, suggesting that the introduction of phenylethynylene group to the phenyl rings of PPAs have made the in general nonemissive PPAs to become highly photoluminescent. Most interestingly, although P1 did not contain any substituent group on its tolane pendant group, it is already highly soluble in common organic solvent and emitting blue fluorescence (416 nm) with a reasonably good quantum yield (0.36). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5483–5498, 2008
Effect of Lewis and Brønsted acids on the homopolymerization of acrylates and their copolymerization with 1‐alkenes
Authors: Luo Rong , Chen Ying , Sen Ayusman
Published: July 2008

The first copolymerization of acrylate and methacrylate with nonpolar 1‐alkenes in the presence of Brønsted acids as complexation agents has been reported. The addition of both homogeneous and heterogeneous Brønsted acids resulted in increased monomer conversion and 1‐alkene incorporation. Further, the heterogeneous Brønsted acids can be recycled without loss of activity. A direct correlation exists between the ability of the Lewis or Brønsted acid to bind to the ester group of the acrylate/methacrylate monomer and its ability to promote the copolymerization reaction. For Lewis acids, there is also a direct correlation between the charge/size ratio at the metal center and their ability to promote copolymerizations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5499–5505, 2008
Synthesis and solution properties of well‐defined comb‐on‐comb graft polymers
Authors: Sun Wei , Yu Fengping , He Junpo , Zhang Chao , Yang Yuliang
Published: July 2008

Well‐defined comb‐on‐comb copolymers of styrene, isoprene, and α‐methyl‐styrene are prepared through cascade “grafting‐onto” methods. The polymer main chain is prepared by nitroxide‐mediated radical polymerization while the branches are prepared by anionic polymerization. The “grafting‐onto” approach employs the coupling chemistry of macromolecular anions, such as polystyryllithium, polyisoprenyllithium, or poly(α‐methylstyryl)lithium, toward either benzyl chloride or epoxy ring on precursor backbones. Thus a series of ABA‐, ABB‐, and ABC‐type comb‐on‐comb copolymers are prepared and characterized by gel permeation chromatography equipped with a multi‐angle laser light scattering detector and a viscometer. Unusual “U‐shaped” dependences of radius of gyration, Rg, on molecular weight are observed for comb‐on‐comb products, which are attributable to delayed elution of the densely grafted copolymers from GPC columns. The result also shows that the comb‐on‐comb copolymers exhibit morphologies from hard sphere to cylindrical rod, depending on the length ratio of the main chain to the branches. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5518–5527, 2008
Polymerization of methyl acrylate and as comonomer with ethylene using a bis(imino)pyridine iron(II) chloride/methylaluminoxane catalyst
Authors: Fullana Matthew J. , Miri Massoud J. , Vadhavkar Sameer S. , Kolhatkar Nikhil , Delis Alexander C.
Published: July 2008

This article describes the homopolymerization of methyl acrylate (MA) and its attempted copolymerization with ethylene using three single‐site catalysts. The primary catalyst under investigation is formed from a bis(imino)pyridine iron(II) chloride with methylaluminoxane (1), which is compared with bis(4,5,6,7‐tetrahydro‐1‐indenyl)zirconium dimethyl/tris(pentafluorenyl)borane) (2), and a P,O‐chelated nickel(II) enolate catalyst (3). Catalyst (1) leads to the highest activities exceeding those of catalyst (2) by a magnitude, whereas catalyst (3) results in formation of no polymer. The kinetics of the polymerizations and the effect of the Al/Fe‐ratio and temperature on the activity and molecular weight of the polymers have been determined. In the ethylene/MA copolymerization trials, catalyst (1) produces a blend of the two homopolymers, polymethyl acrylate (PMA) and polyethylene. Remarkably, using catalyst (1) it is possible to produce polymer blends with up to 52% PMA at relatively high activities. The polymerization kinetics has been determined based on the directly measured uptake of ethylene during the runs. NMR spectroscopy, DSC and GPC measurements have been used as efficient methods to prove that polymer blends instead of true copolymers were formed. Finally, some conclusions about the polymerization mechanism will be drawn. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5542–5558, 2008
Synthesis and characterization of asymmetric centipede‐like copolymers with two side chains at each repeating unit via ATRP and ring‐opening polymerization
Authors: Shi Gang‐Yin , Zou Peng , Pan Cai‐Yuan
Published: July 2008

A series of well‐defined centipede‐like copolymers with poly(glycidyl methacrylate) (PGMA) as main chain and poly(L‐lactide) (PLLA) and polystyrene (PSt) as side chains have been synthesized successfully by combination of ring‐opening polymerization and atom transfer radical polymerization (ATRP). The synthetic process includes three steps. (1) Synthesis of PGMA via ATRP; (2) preparation of macroinitiator with one bromine group and a hydroxyl group at every GMA unit of PGMA; (3) ring‐opening polymerization of LLA and ATRP of St to obtain the asymmetric centipede‐like copolymers. The number–average degrees of polymerization of PGMA backbone, PLLA and PSt side chains were determined by 1H‐NMR spectra, and the molecular weights of the resultant intermediates and centipede‐like copolymers were measured by gel permeation chromatography. The molecular weight distributions were narrow and the molecular weights of both the backbone and the side chains were controllable. The thermal behavior of the centipede‐like copolymers was investigated by differential scanning calorimeter. With the increase of PSt side chain length, the glass transition temperature of PLLA side chains shifted to high temperature, and crystallization ability of PLLA side chains became poor. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5580–5591, 2008
Carbazolevinylene‐based polymers and model compounds with oxadiazole and triphenylamine segments: Synthesis, photophysics, and electroluminescence
Authors: Vellis Panagiotis D. , Mikroyannidis John A. , Cho Min Ju , Choi Dong Hoon
Published: July 2008

Two new soluble alternating carbazolevinylene‐based polymers POXD and PTPA as well as the corresponding model compounds MOXD and MTPA were synthesized by Heck coupling. POXD and MOXD contained 2,5‐diphenyloxadiazole segments, while PTPA and MTPA contained triphenylamine segments. All samples displayed high thermal stability. The polymers had higher glass transition temperature (Tg) than their corresponding model compounds. The samples showed absorption maximum at 364–403 nm with optical band gap of 2.62–2.82 eV. They emitted blue‐green light with photoluminescence (PL) emission maximum at 450–501 nm and PL quantum yields in THF solution of 0.15–0.36. The absorption and the PL emission maxima of PTPA and MTPA were blue‐shifted as compared to those of POXD and MOXD. The electroluminescence (EL) spectra of multilayered devices made using four materials exhibited bluish green emissions, which is well consistent with PL spectra. The EL devices made using poly(vinyl carbazole) doped with MOXD and MTPA as emitting materials showed luminances of 12.1 and 4.8 cd m−2. POXD and PTPA exhibited 25.4, and 96.3 cd m−2, respectively. The polymer containing the corresponding molecules in the repeating group showed much higher device performances. Additionally, POXD and MOXD exhibited better stability of external quantum efficiency (EQE) and luminous efficiency with current density resulting from enhancing the electron transporting properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5592–5603, 2008
Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach
Authors: Hussain H. , Tan B. H. , Gudipati C. S. , Liu Y. , He C. B. , Davis T. P.
Published: July 2008

Amphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by1H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and1H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by1H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008