Polymer Journal

A series of amphiphilic diblock copolymers (PVAm-b-PVPin: AmPn = A82P6, A72P26, and A70P74) with different block lengths of hydrophilic poly(vinyl alcohol) (PVA, A) and hydrophobic poly(vinyl pivalate) (PVPi, P) blocks were prepared. AmPn was synthesized from a poly(vinyl acetate)-b-P (PVAc-b-P) diblock copolymer by selectively hydrolyzing the pendant acetyl groups in PVAc. In water, AmPn polymers formed spherical polymer micelles with a PVPi core and a PVA shell due to hydrophobic interactions between the PVPi blocks. The hydrodynamic radius (Rh), light scattering intensity (LSI), and aggregation number (Nagg) of AmPn increased with increasing PVPi block length. Conversely, the critical micelle concentration (CMC) was reduced due to stronger hydrophobic interactions. This study promotes potential applications for AmPn micelles to be used as nanocarriers for hydrophobic anticancer drugs. A series of amphiphilic diblock copolymers (PVAm-b-PVPin: m/n = 82/6, 72/26, and 70/74) with different block lengths of hydrophilic poly(vinyl alcohol) (PVA) and hydrophobic poly(vinyl pivalate) (PVPi) blocks were prepared. PVAm-b-PVPin was synthesized from poly(vinyl acetate)-b-PVPi (PVAcm-b-PVPin) diblock copolymer via selectively hydrolysis. In water, PVAm-b-PVPin formed spherical polymer micelles with a PVPi core and a PVA shell. The hydrodynamic radius, light scattering intensity, and aggregation number of PVAm-b-PVPin increased with increasing PVPi block length. In contrast, the critical micelle concentration was reduced because of stronger hydrophobic interactions.

Heptaisobutyl-norbornenylethyl-substituted cage octasilsesquioxane (POSS) (1a) and heptaphenyl-norbornenylethyl-substituted POSS (1b) were subjected to ring-opening metathesis polymerizations (ROMP) at room temperature with the Grubbs 2nd generation catalyst. The metathesis polymerizations of 1a and 1b were performed at room temperature for 3 h with initial monomer molar concentrations of [1a, 1b] = 10 mM, and the number average molecular weights (Mn) of 2a and 2b were 82,000 g/mol and 87,000 g/mol, respectively. Dynamic light scattering (DLS) and static light scattering (SLS) measurements showed that the Rg/Rh value for 2a was 4.91, suggesting the formation of polydisperse rod-shaped particles. Chloroform solutions of 2a and 2b were cast onto glass substrates and dried at room temperature to obtain optically transparent free-standing films. X-ray diffraction (XRD) analyses of the casted films revealed their amorphous natures. Thermogravimetric analyses (TGA) of 2a and 2b under N2 atmospheres showed 5 wt% losses (Td5) at 416 °C and 451 °C, respectively. The POSS-pendant polynorbornenenes connected with short spacers exhibited showed high optical transparencies owing to the prevention of POSS crystallization and the excellent thermal stability. Side-chain typed POSS-based polynorbornenes connecting with a short spacer exhibiting optical transparency owing to prevention of POSS crystallization to provide amorphous character. In addition, the resulting amorphous polymers exhibited excellent thermal stability.