PEO, macromonomer

Poly(ethylene oxide). The synthesis and subsequent hydrolysis and condensation of alkoxysilane-terniinated macromonomers have been studied (39,40). Using Si-nmr and size-exclusion chromatography (sec) the evolution of the siUcate stmctures on the alkoxysilane-terniinated poly(ethylene oxide) (PEO) macromonomers of controlled functionahty was observed. Also, the effect of vitrification upon the network cross-link density of the developing inorganic—organic hybrid using percolation and mean-field theory was considered. 

They obtained moderately monodispersed (1.2 + 0.1) polymacromonomers with 30% initiator efficiency when short macromonomers (DP = 21 to 75) are polymerized. Higher MW macromonomers polymerized only partially. Evidence for interaction of the PEO ether groups with the catalytic center is given and assumed to be responsible for the shortcomings of the living system. Random and block copolymers of PS and PEO macromonomers, as well as of P(EO-b-S) and P(S-b-EO) macromonomers have also been made [112], The same group successfully prepared PS macromonomers with a norbornene group in the a position [113]. 

In this review we summarize and discuss the amphiphilic properties of polyoxyethylene (PEO) macromonomers and PEO graft copolymer molecules, the aggregation of amphiphilic PEO macromonomers into micelles, the effect of organized aggregation of macromonomers on the polymerization process, and the kinetics of radical polymerization and copolymerization of PEO macromonomer in disperse (dispersion, emulsion, miniemulsion, microemulsion, etc.) systems [1-5]. 

Kawaguchi et al. [12] have modified Paine s model for the dispersion copolymerization of amphiphilic PEO macromonomers. The authors have modeled the variation of the particle size and its distribution with reaction conditions. For example, the expressions for the critical conversion (x Xthe particle radius (r), and the surface area (S) occupied by a PEO chain are as follows ... 

Poly(ethylene oxide) (PEO) macromonomers constitute a new class of surface active monomers which give, by emulsifier-free emulsion polymerization or copolymerization, stable polymer dispersions and comb-like materials with very interesting properties due to the exceptional properties of ethylene oxide (EO) side chains. They are a basis for a number of various applications which take advantage of the binding properties of PEO [39], its hydrophilic and amphipathic behavior [40], as well as its bio compatibility and non-absorbing character towards proteins [41]. Various types of PEO macromonomers have been proposed and among them the most popular are the acrylates and methacrylates [42]. 

The microviscosity of PEO micelles is comparable to that of SDS. To explore the possibility of specific interactions between pyrene and the PEO group, H-NMR spectra were measured for the PEO macromonomers (C1-(EO)57-C7-VB) in the presence and absence of pyrene. The spectra did not show any evidence of... 

The aggregation numbers Nagg is determined as 27 for C1-(EO)53-C4-VB and 38 for Cr(EO)53-C7-VB micelles by analysis of fluorescence curves. A micelle formation mechanism is proposed for nonionic polymeric surfactants with weakly hydrophobic groups. At low concentrations of PEO macromonomers, large loosely aggregated structures involving the PEO chains are formed. At higher concentrations normal micelles form. These are star-shaped, with a hydrophobic core surrounded by a corona of PEO chains. 

The analysis of the reaction serum (the continuous phase without polymer particles) at the end of polymerization led to the conclusion that the molecular weight of the soluble oligomers of styrene and PEO macromonomer varied from 200 to 1100 g mol-1. This indicates that the critical degree of polymerization for precipitation of oligomers in this medium is more than ten styrene units and only one macromonomer unit per copolymer chain. Several reasons for the low molecular weight of the soluble copolymers were proposed, such as the thermodynamic repulsion (or compatibility) between the PEO chain of the macromonomer and the polystyrene macroradical, the occurrence of enhanced termination caused by high radical concentration, and, to a lower extent, a transfer reaction to ethanol [75]. 

The colloidal stable polymer dispersions, the monodisperse polymer particles, and high conversions (85-100%) can be obtained with most of the other macromonomers (MAL,VB, and MA) of PEO (MW>PEO=2000)) [76]. Also, when macromonomers are used (3.1 wt% based on styrene), there is practically no coagulum produced. This is not the case in the presence of polymerizable PEO surfactants (surfmer I R1=CH3(CH2)11-, R2=H, n=34 and surfmer II R =CH3 (CH2)n-, R2=H, n=42) despite the higher amounts of stabilizer used (up to 60 wt% of coagulum). Furthermore, the particles are more monodisperse with PEO macromonomer (Dw/Dn=1.025 for PEO-MA and 1.13 for PVPo) compared to those with surfmer. Comparatively poorer results were obtained with conventional surfactants such as ethoxylated nonylphenol, even when used in large amounts. 

The preparation of monodisperse micronsized polymer particles by radical dispersion copolymerization of styrene with PEO macromonomers having p-styrylbutyl endgroup (Mn=2000) in methanol/water (90/10, v/v) and modeling of colloidal parameters were shown in [12,78]. The polymer particle diameter varied within the range 0.3-0.5 pm. The dependence of the particle size on the experimental conditions was modeled into the expression... 

Copolymerization of PEO Macromonomers with Alkyl Acrylates and Methacrylates... 

Gramain and Frere [82] observed that the free radical polymerization of co-meth-acryloyl terminated PEO macromonomers in the aqueous phase deviates from the solution polymerization. Polymerizations initiated by KPS in water were much faster than those that proceeded in the solution. Low molecular weight polymers were formed in the aqueous systems (ca. up to 20 macromonomer units were incorporated into polymer molecules). 

It has been suggested that the mechanism of bead formation occurring in the PEO macromonomer system is quite different from the mechanism proposed by Dimonie et al. [109] for ISP of acrylamide. According to these authors, phase inversion occurs after the start of the reaction. At high conversions, the gel breaks under stirring into small particles which remain as such until the end of polymerization. With PEO macromonomers, beads are present from the beginning up... 

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