摘要:

AbstractDiazosulfonates are water soluble, highly photoactive but thermally stable compounds which are prepared from appropriate diazonium salts and sodium sulfite in a diazo coupling reaction. Upon irradiation, the stabletrans‐isomer is converted into the instablecis‐isomer, followed by decomposition via a radical or an ionic mechanism with phenyl radicals or diazonium salts, respectively, as intermediates, depending on the reaction conditions. These chromophores could be incorporated as side groups into polymers via copolymerization, copolycondensation or via polymer analogous reaction. Reaction conditions as well as advantages and disadvantages of these different techniques and the photochemistry of the polymers are discussed. Diazosulfonate polymers have been applied successfully as photoresins in offset printing techniques. The use in test stripes in quick assays for the detection of phenolic compounds is discussed based on the coupling reaction of the diazonium salt intermediates. In addition, diazosulfonate containing surfactants could be synthesized and were used as photoactive stabilizers in emulsion polymerization and as partners in photoactive polyelectrolyte‐surfactant comp

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980801

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractEnthalpy relaxation due to physical aging of hydroxyl‐terminated poly(ether sulfone)s (PES) with various molecular weights was studied by DSC at three aging temperatures betweenTg− 45°C andTg− 10°C. The experimental results revealed that both the average enthalpy relaxation time 〈τ〉 and limiting enthalpy relaxation ΔH∞decrease slightly with increasing molecular weight for PESs aged at the same temperature intervalsTg−Ta(whereTa

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980802

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractSeveral new vinyl and allyloxybenzoate steroidal‐based mesogens were synthesized and attached to cyclic tetramethylhydrosiloxane rings using standard hydrosilation chemistry. The steroids examined, all derivatives of cholesterol, 3β‐hydroxy‐24α‐ethylcholest‐5,22‐diene, 3α‐hydroxyandrostan‐17‐one, 3β‐hydroxyandrostan‐17‐one, and 3β‐hydroxypreg‐5‐en‐20‐one were chosen because structural variations in the 17‐β aliphatic chain of the tetracyclic core were present. The synthesis and phase behavior of these mesogenic compounds are discussed with respect to previous systematic investigations linking structural features to mesomorphic behavior. Macromolecular cyclic siloxanes derivatized with these steroidal mesogens were characterized for liquid crystallinity using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and X‐ray diffraction. Compounds with 17‐β ketone substituents possessing vinylbenzoate spacer groups do not exhibit liquid crystallinity, whereas similar compounds with allyloxybenzoate spacer units exhibit broad smectic mesophases. The ability to from partially or fully interdigitated layered mesophases with respect to the 17‐β substituent is examined using X‐ray diffraction. The results indicate the length and flexibility of the 17‐β group must be considered along with the na

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980803

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractAn investigation on the effect of the variation of the amount and the structure of cocatalyst and of polarity of the solvent on propene/1‐hexene copolymerization with the isospecific catalystrac‐[ethylenebis(1‐indenyl)]zirconium dichloride (rac‐(EBI)ZrCl2) was performed. A noticeable enhancement of copolymerization activity and a moderate increase of the molecular weights were observed with increasing MAO/Zr ratio as well as upon mixing methylaluminoxane (MAO) and AliBu3, while isotacticity and comonomer composition are not affected by such variations. On the other hand, a gradual increase in CH2Cl2content in the CH2Cl2/toluene solvent mixture, which greatly increases the copolymerization activity, noticeably influences the molecular weight and sensibly enhances the 1‐hexene comonomer content. The formation of cationic active species, separated from their counterions, might be the cause of the better accessibility of the active sites for the bulkier

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980804

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractCompositional analysis of a series of free‐radical emulsion polymerized styrene/2‐ethylhexyl acrylate copolymers following close to random polymerization statistics was accomplished by elemental analysis, UV and IR. A satisfactory agreement was obtained between the three independent techniques. IR calibration curves were constructed based on sequence‐independent infrared absorption bands determined by plotting peak intensities against the number fraction of each of the possible monad, dyad and triad structures in the copolymers. The intensities of the skeletal ring breathing vibration of styrene units at 1 602 cm−1as well as the CO stretching vibration of the saturated ester group of 2‐ethylhexyl acrylate units at 1158 cm−1were shown to be representative of the copolymer composition, whereas the position and shape of the carbonyl stretching band at 1730 cm−1were shown to depend on both the composition and the monomer sequence distribution. A calibration curve not requiring the use of an internal thickness band was obtained by plotting the ratio of absorbances of the 1 602 cm−1and the 1 158 cm−1peaks as a function of the mole ratio of the corresponding monome

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980805

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPoly(ether ketone)s containing 1,3‐dicyclohexyl‐1‐methyl‐3‐phenylindan groups in the main chain were prepared from different bisphenols and a bisfluoride monomer which contains the indan group. The bisfluoride monomer was synthesized in a three‐step process, starting from cyclohexyl phenyl ketone. All polymers are soluble in tetrahydrofuran, chloroform andN,N‐dimethylpropyleneurea. No melt transitions were detected by differential scanning calorimetry. Glass transition temperatures are relatively high (218°C to 255°C). In gel‐permeation chromatography with polystyrene calibration, 8400

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980806

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractThe influence of argon plasma on polycarbonate (PC) and poly(propylene) (PP) has been studied in terms of structural changes and reaction mechanisms.In situUV‐visible ellipsometry reveals formation of a surface layer with a higher refractive index than the untreated polymer. The increase in the refractive index is attributed to polymer densification, which is assigned to crosslinking. However, a decrease in the average molecular weight of the PC is also observed and two populations of macromolecules of different size are detected by light scattering measurements, revealing a competition between crosslinking and degradation. The reaction mechanisms were investigated using Nuclear Magnetic Resonance (1H NMR) andin situIR ellipsometry. Degradation is caused by carbonate bond breaking, while crosslinking seems to be related to a decrease in methyl groups. The ellipsometry results are correlated with amorphous phase extraction and1H NMR analysis of modified PP. The crosslinking mechanism involves the elimination of methyl groups, and also the formation of exomethylenic bonds. Spectroscopic ellipsometry appears to be a valuable tool to study the interaction between a plasma and a polymer, as UV‐visible ellipsometry is sensitive to structural changes in the polymer, while IR ellipsometry detects the appearance and disappearance of chemical groups in a surface la

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980807

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractPoly(ethylene oxide)s having a primary or secondary amino group at one chain end have been synthesized by direct anionic polymerization of ethylene oxide initiated by aminoalcoholates. The ring opening reaction of ethylene oxide by the amino group could be avoided when the alcoholate was reactive enough, that is, with potassium alcoholates in dry aprotic medium (THF). In this case, a living anionic polymerization of ethylene oxide occurred, with full conversion of the monomer. This is shown by the NMR and molecular weight characterizations of the polymers and kinetic studies of the polymerization.

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980808

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractRadical copolymerizations of allyla‐(N‐maleimido)acetate (AMI) with styrene (D, electron‐donor) or maleic anhydride (A, electron‐acceptor) were carried out in benzene and/or methyl ethyl ketone (MEK) at 50–70°C in the presence of 2,2′‐azoisobutyronitrile (AIBN) as initiator. The structure and properties of copolymers synthesized were derived from IR, chemical, DTA and TGA analyses. Side‐chain unsaturation of macromolecules was also proved by the crosslinking effect observed. Kinetic parameters of copolymerization such as complex‐formation (Kc), cyclization (kcyc), and copolymerization constants and ratios of chain growth rates for the participation of monomer charge transfer complexes (CTC) and free monomers for both systems were obtained:Kc= 0,20 ± 0,01 and 0,05 ± 0,005 L/mol in CH3COOH‐d4at 35 ± 0,1°C (1H NMR method) forD…AMI and AMI…Acomplexes, respectively;kcyc· 105= 1.71 and 0,66 L/(mol · s),r1= 0,13 ± 0,01 and 0,037 ± 0,002,r2= 0,048 ± 0,002 and 0,052 ± 0,002 (by Kelen‐Tüdőş method),k12/k21= 0,20 and 0,62,k1c/k12= 0,6 and 29,8,k2c/k21= 4,8 and 9,1 for theD‐AMI and AMI‐Asystems, respectively. The results show that alternating cyclocopolymerization reactions are realized which are carried out via a “mixed” mechanism in theD‐AMI system and via a “complex” mechanism in the AMI‐Asystem, with formation of cyclolinear macromolecules containing side‐chain unsaturated fragments of “allyl” (D‐AMI copolymer) and “imide” (AMI‐Acopolymer) types. The synthesized copolymers easily undergo crosslinking by thermotreatment (105°C, 30 min) and/or by UV

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980809

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY

摘要:

AbstractNovel types of methoxy poly(ethylene glycol) (PEG) linkers (U‐PEG linkers) have been synthesized. These PEG linkers are linear polymers that attach to bioactive agents via a functional group, derived from a 2° alcohol, located in the center of the polymer chain versus the traditional terminal attachment site. These new types of linkers can be prepared with different functional groups (e.g. active ester, succinimidyl carbonate, and carbazate) for selected point of attachment, including ethylene oxide oligomers to provide “stems” when steric factors need to be addressed. Conversion ofp‐nitrophenyl carbonates to the more desirable succinimidyl carbonates has also been accomplished by a novel nucleophilic displacement procedure. Modification of proteins with these reagents is easily accomplished and is illustrated by the conjugation of a U‐PEG linker withL‐

ISSN:1022-1352    

DOI:10.1002/macp.1997.021980810

出版商:Hüthig&Wepf Verlag    

年代:1997

数据来源: WILEY