PMMA-PBA

Mori, S., Determination of Chemical Composition and Molecular weight distributions in high-conversion Styrene methyl methacrylate copolymers by liquid adsorption and Size exclusion chromatography. Anal. Chem, 60,1125 (1988). Montaudo, M.S. and Montaudo, G., Bivariate Distribution in PMMA/PBA Copolymers by combined SEC/NMR and SEC/MALDI measurements, Macromol-ecules, 32, 7015 (1999). 

Montaudo, M. S. and Montaudo, G, Bivariate Distribution in PMMA/PBA Copolymers by Combined SEC/NMR and SEC/MALDI Measurements, Macromolecules, 32, 7015,1999. 

To extend the )plications of LC-NMR, we have further examined the compositions and blockiness of various polymer mixtures, including pBA and polybutadiene, where 1,4-butadiene, 1,2-butadiene and BA were identified by their unique H chemical shifts at tqrproximately 5.35, 4.95 and 3.98 ppm, respectively. In reverse-phase HPLC with the same solvent gradient conditions as above, homopolymer pBA and polybutadiene eluted at 21.76 and 34.20 min., respectively. TTie random copolymers of p(MMA/BA) and p(MMA/Sty) both eluted between 8 and 18 minutes. Owing to their hydrophobicity, the hi er the percentage of BA and styrene in the copolymer, the longer the retention time. Figure 5 illustrates the LC separation of pMMA, pBA, p(MMA/BA) and p(BA-b-MMA) by a reverse-phase column. A comparison of p(MMA/BA) random copolymer (retention time 13.9 min.) to p(BA-b-MMA) block copolymer (retention time 18.3 min.) with similar composition shows that the block copolymer interacted more with the C-18 stationary phase and eluted at a later time. This result demonstrated that the retention of p(MMA/BA) copolymer by reverse-phase LC is predominately influenced by die pBA portion of dre copolymer. The block copolymer, which mimics the homopolymer pBA, is mote hydrophobic and retained more on die C18 colunm than the random copolymer. The excellent LC separation permits us to quantitatively determine... 

Figure 5. The reverse phase HPLC chromatograms of the mixture of pMMA, pBA, p(MMA/BA) and p(BA-b-MMA) with ELS and UV detections. The SUPELCOSIL Octadecyl column (25cm x 4.6mm ID) was used with acetonitrile/THF solvent gradient (flow rate Iml/min).

Aside from the PS-PBA type of emulsion FRRPP product introduced in Section 3.2, it is worth mentioning the promise of the formation of other emulsion FRRPP block copolymer products, such as PMMA-PBA. 

Dufor Bruno, Konynov Kaloian, Pakula Tadeusz, and Matyjaszewski Krzysztow. PMMA-PBA 3-arm star block copolymer thermoplastic elastomer. AfacromoZ. Chem. Phys. 209 no. 16 (2008a) 1686-1693. 

Figure 5.12 Scheme of PMMA/PBA core-shell particles, undeformed (a) and deformed with fibrillation in the shell (b) [12]... 

Montaudo M. Bivariate distribution in PMMA/PBA copolymers by combined SEC/ NMR and SEC/MALDl measurements. Abstr Papers Am Chem Soc 2000 219. U392-U392. 

The combination of SEC-MALDI and SEC-nuclear magnetic resonance (NMR) enabled the bivariate distribution to be determined. Two random polymethylmethacrylate (PMMA)/polybutyl acrylate (PBA), obtained at low and high conversions were investigated [10]. SEC-NMR data allowed the computation of the fractions composition whereas SEC/MALDI data provided the molar masses estimates, respectively. Bivariate distribution maps are prepared from this data as shown in Figure 5.4. Typical results for high conversion PMMA-PBA copolymer are shown in Table 5.1. 

Depending on the chemical structure of the MAI, a suitable solvent is sometimes needed to get a homogenous state of reaction mixture. Even if using the same combination of comonomers, for example, to prepare PMMA-b-poly(butyl acrylate) (PBA), the selection of the using order of comonomers for the first step or second step would affect the solvent selections, since PMMA is not easily soluble to BA monomer, while PBA is soluble to MM A monomer [28]. 

PMMA-b-PBA shows improved izod impact strength compared to PMMA homopolymer (41). Polyisobutylene (PIB) or its hydrogenated one (PIB-H) also acts as an impact modifier [31]. PSt-b-PIB, PSt-b-PIB-H, and PMMA-b-PIB-H derived from MAI have high- and wide-range molecuiar weight and show high flexibiiity and flow property [42]. The improved flexibiiity of PMMA-b-PEG synthesized as an elastomer, was confirmed by dynamic viscoelastic measurement [43]. 

Fig. 3.5. TEM image of a cut through a SAN matrix with incorporated core/double shell particles, dark core PMMA bright area PBA shell diameter of the particlesof the first shell about 220 nm the second PMMA shell is compatible with SAN matrix, therefore the contrast is very weak (details see references at the end of Chap. 3)...

The copolymer composition in miniemulsion copolymerization of vinyl acetate and butyl acrylate during the initial 70% conversion was found to be less rich in vinyl acetate monomer units [34]. Miniemulsion polymerization also allowed the synthesis of particles in which butyl acrylate and a PMMA macromonomer [83, 84] or styrene and a PMMA macromonomer [85] were copolymerized. The macromonomer acts as compatibilizing agent for the preparation of core/shell PBA/PMMA particles. The degree of phase separation between the two polymers in the composite particles is affected by the amount of macromonomer used in the seed latex preparation. 

Fig. 19a,b. TEM of armored latexes a sealed clay on PBA template particles b sealed clay on PMMA template particles after removal of the PMMA in the core... 

Core-shell nanoparticles can also be fabricated using microemulsions. This was performed using a two-stage microemulsion polymerization beginning with a polystyrene seed [62]. Butyl acrylate was then added in a second step to yield a core-shell PS/PBA morphology. The small microlatex led to better mechanical properties than those of similar products produced by emulsion polymerization. Hollow polystyrene particles have also been produced by microemulsion polymerization of MMA in the core with crosslinking of styrene on the shell. After the synthesis of core-shell particles with crosslinked PS shells, the PMMA core was dissolved with methylene chloride [63]. The direct cross-... 

The greater degree of freedom enjoyed by the 1-naphthyl label in P/VN is most likely ascribable to motion independent of the polymer chain about the bond of attachment. Since the vectors for absorption and emission are located within different planes within the molecular framework for triplet emission, such motions constitute a mechanism of enhanced depolarization for the P/VN system. In the case of PMMA it has been shown (H) that independent motion of a 1-VN label occurs in the vincinity of the relaxation of the polymer but is characterized by an apparent activation energy inferior to that sensed by an ester label or as afforded by dielectric and dynamic relaxation data for the g-process. Consequently whilst the onset of motion might be consistent with an increased degree of free volume released by the g-mechanism, the activation energy for naphthyl group reorientation within the lifetime of the excited states should not be equated with that of the g-process itself in PBA. 

Fig. 18. Temperature dependencies of the real ((. ) and imaginary (( .") component of the shear modulus measured at the deformation frequency of lOrad/s for the pure and tapered triblock copolymers pMMA-b-pBA-b-pMMA and p(MMA-grad-BA)-b-pBA-b- p(MMA-grad-BA) of approximately the same overall composition, MW and polydispersity DSC traces are shown to help localize the glass transition temperatures (T ) of the microphases. Reprinted with permission from [94]. Copyright (2000) John Wiley Sons, Inc.

Table 3. Series of 3-Arm Star PBA-PMMA bloek copolymers...

Figure 7 SAXS of 3-arm stars PBA-PMMA block copolymers after thermal...

Tensile behavior is of primary importance when considering the properties of a thermoplastic elastomer. The stress-strain dependencies for the 3-arm star PBA-PMMA block copolymers listed in Table 3 are shown in Figure 8. The data were recorded at room temperature and with drawing rate of 5 mm/min. 

Similarly, poly-Cf-methylstyrene is miscible with PMMA, PEMA, PBMA, and PCHMA. Poly-p-methylstyrene, and poly-p-t-butylstyrene show miscibility with polyalkyl(meth)acrylates. However, PS is immiscible with PMMA, PMA, polyethylacrylate (PEA), polybutylacrylate (PBA), or PBMA [Somani and Shaw, 1981],... 

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