ISSN:0007-1641    

DOI:10.1002/pi.4980210202

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPhotoresponsive macromolecules are of interest both as novel organic materials for applications in photodevices and as models for photomodulated biological processes. The presence in polymer chains of photosensitive groups and of chiral groups capable of inducing optical activity into the polymer is very useful for the analysis of photomodulated structural variations and allows storage of the light effect in the form of chiral information. Polypeptides bearing photochromic groups in the side chains are very convenient as the chiroptical properties of the peptide chromophore can be correlated to the backbone conformation. Thus polymers of L‐aspartic acid, L‐glutamic acid and L‐lysine with azobenzene or stilbene groups attached covalently to the side chains are discussed in terms of photoinduced conformational changes and chiroptical information storage in the spectral region of the peptide and of the photoresponsive chromophore. Optically active photochromic macromolecules with hydrocarbon backbone, such as copolymers of (—)‐menthyl acrylate with vinyl or acryloyl derivatives of azobenzene, stilbene and indolinospirobenzopyran, also show in some cases photodependence of chiroptical properties with evidence of at least local conformational changes as a consequence of light irradiation which can be used for chiral in

ISSN:0007-1641    

DOI:10.1002/pi.4980210203

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractReactive microgels are considered as soluble intramolecular cross‐linked macromolecules, with sizes comparable to linear or branched macromolecules and reactive groups at their surface or interior. This article is the written version of a Macrolux 1988 lecture. It presents the history and some more important results and relationship of synthesis, characterization and properties of this group of polymers and refers briefly to applicatio

ISSN:0007-1641    

DOI:10.1002/pi.4980210204

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA study of the crosslinking reactions in silane modified polyethylenes has been completed. Crosslinking of ethylene‐vinyl trimethoxy silane copolymers during high temperature melt processing has been investigated using melt rheological and infrared spectroscopic techniques. Two environmental factors are shown to influence crosslinking formation, namely oxidation of the polymer and the presence of di‐n‐butyl‐tin dilaurate, a condensation catalyst. These are believed to initiate high temperature crosslink formation via different non‐interacting mechanisms. It is deduced that silane crosslink formation as a result of oxidation is due to intramolecular interaction of oxidised polyethylene and pendant methoxy silane branches. Observation of a hydrogen bonded silanol intermediate species is consistent with this h

ISSN:0007-1641    

DOI:10.1002/pi.4980210205

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe catalytic oxidation of 2‐mercaptoethanol was investigated kinetically for the system cobalt(II)phthalocyanine‐tetra (sodium sulphonate) in the presence of poly(quaternary ammonium salts) at pH = 8.85. From a comparison with other kinetic data a reaction mechanism could be proposed in which the specific effects of the polyelectrolyte become manifest. The effect of ionic strength on the catalytic activity was also studied.The soluble catalytic system was immobilized on latex particles by using a polymeric soap containing quaternary ammonium groups. The latex particles with the ammonium groups at the surface were used to bond the cobalt catalyst by ionogenic interaction. Using this latex supported polymeric catalyst the activity of its homogeneous counterpart could be maintained while at the same time immobilization was accomplis

ISSN:0007-1641    

DOI:10.1002/pi.4980210206

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractInorganic submicron particles, such as TiO2, were modified with titanate coupling agents. The structure and stability of some titanates, both in solution and at the particle surface, were investigated by various methods. The modified titanium dioxide was dispersed in a solution of sodium dodecylsulphate (SDS) in water. The surfactant adsorbs at the now hydrophobic particle surface, thus creating a micellelike structure with an inorganic particle in the centre. In this system an emulsion polymerization of methyl methacrylate was carried out. Product formed at the particle surface is either physically bound by entanglement or chemically bound by covalent bonding to the titanates. In this way a core‐shell morphology is obtained with an inorganic core and a polymer shell. The effects of several reaction parameters on the kinetics of the polymerization were studied. The encapsulated TiO2particles may offer interesting prospects in those applications where good coupling between polymer matrix and inorganic particles is necessary, such as latex paints and polymer composite material

ISSN:0007-1641    

DOI:10.1002/pi.4980210207

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractPoly(ethylene terephthalate) (PET) Mylar® samples were treated by corona discharge in order to improve their adhesive properties. The corona treatments were performed in different atmospheres including nitrogen, ammonia and air.X‐ray photoelectron spectroscopy (XPS) was used to investigate the chemical modifications induced at the PET surface by these corona treatments. XPS results show that nitrogen incorporation takes place in the form of non‐oxygenated nitrogen functionalities, like amine or cyano groups. These are present at the surface of all the corona‐treated samples but in different concentrations depending on the gases used in the corona discharge. Furthermore, XPS analyses performed after heating of the treated samples show a higher thermal stability of the corona‐induced surface modifications in the case of nitrogen and ammonia.Ion scattering spectroscopy (ISS) and static secondary ion mass spectroscopy (SIMS) analyses were also performed because of their higher surface sensitivity compared with XPS: ISS reveals that nitrogen is not present at the topmost surface layer of the treated samples but is incorporated just beneath. The outermost surface layer presents a composition rich in oxygen. Finally, static SIMS spectra show that corona treatment induces more surface degradation when performed in air compared with nitrogen or ammonia.These results are discussed in relation to adhesive propertie

ISSN:0007-1641    

DOI:10.1002/pi.4980210208

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractSeveral commercial polymers—poly(ethylene) (PE), poly(propylene) (PP), poly(vinylidene fluoride) (PVF2), poly(vinyl chloride) (PVC) and polystyrene (PS)—were treated in air with an argon‐fluorine UV excimer laser (λ = 193 nm).The polymer etch rate was investigated by two methods: quartz crystal microbalance (QCM) and piercing of films.X‐ray photoelectron spectroscopy (XPS) analysis was performed on the modified surfaces after laser exposure at various fluences. Samples were subsequently analysed by scanning electron microscopy (SEM).From our results, polymers may be classified into two categories concerning their reactivity towards UV laser light.— the weakly absorbing polymers (e.g. PE, PP, PVF2) where a photothermal process (thermal degradation) dominates the interaction.— the strongly absorbing polymers (e.g. PVC, PS) where a photochemical process (photoablation) dominates the

ISSN:0007-1641    

DOI:10.1002/pi.4980210209

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe surface composition of films obtained from acrylic latexes (45 wt% MMA, 55 wt% BuA) stabilized by two anionic surfactants (either sodium dodecyl sulphate (SDS) or sodium dodecyl diphenyl ether disulphonate (SDED) has been studied by attenuated total reflection with Fourier transformed infrared spectroscopy (ATR‐FTIR), X‐ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The results of this surface analysis are summarized and used to interpret adhesion properties of the films on glass substrate. Adhesion properties were derived from peeling tests. In the case of SDED, the peel strength increases with surfactant surface concentration. This is due to strong polar interactions between the hydrophilic part of the surfactant and the polar groups of the glass surface and to the anchorage of the hydrophobic part of the surfactant in the copolymer matrix. In the case of SDS, the peel strength decreases with increasing surfactant surface concentration. The same polar interactions as with SDED exist, but the SDS layer at the interface is very thick. It forms what is called a ‘weak boundary layer’ in which rupture propagates

ISSN:0007-1641    

DOI:10.1002/pi.4980210210

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA detailed study of the photopolymerization ofN,N‐didodecylmethylethylmethacrylate ammonium chloride, a reverse micelle forming surfactant, is presented. The polymerization was photochemically initiated at 350 nm using AIBN andp‐AIBN as initiators. However, the polymerization could also be initiated through direct excitation of the methacrylate group. High rates of polymerization resulted because of the organization of the monomer in reverse micellar assemblies. The molecular weights of the polymer decrease with increasing initiator concentration and are always larger than the molecular weight of the reverse micelle.The properties of the monomeric reverse micellar system are compared with those of the polymeric system and show that the dynamic character of the reverse micellar system can be lowered upon polymerization. The properties of the polymeric aggregates, however, differ if a given amount of water is solubilized before or after polymerization. The mean aggregation number of the monomeric and polymeric aggregates as well as the aggregation behaviour of both systems are compared. This comparison suggests that a polymeric aggregate consists of more than one polymer ch

ISSN:0007-1641    

DOI:10.1002/pi.4980210211

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY