Poly(lactic acid) (PLA)/poly[(butylene adipate)-co-terephthalate] (PBAT) blends were fabricated by melt blending, with 2,2′-(1,3-phenylene)bis(2-oxazoline) (BOZ) and phthalic anhydride (PA) used as compatibilizers. It was found that a small amount of BOZ or PA greatly increased the elongation at break of the PLA/PBAT blends without sacrificing their high tensile strength. Scanning electron microscopy results revealed that the PBAT particles became finer and were uniformly dispersed in the matrix when the compatibilizers were incorporated, which indicated that the interfacial bonding and compatibilization between PLA and PBAT were improved in the presence of the compatibilizers. Compared with PLA/PBAT blends, the molecular weight of PLA/PBAT/PA/BOZ blends was increased due to chain-extending reactions. Differential scanning calorimetry results suggested PBAT decreased the crystallization rate and crystallinity of PLA in the blends. Moreover, the glass transition temperature of PBAT was further decreased when the compatibilizers were used. © 2013 Society of Chemical Industry

Hyperbranched copolymers with different degrees of branching (DBs), poly(3,4-dihydroxycinnamic acid)-co-poly(4-hydroxycinnamic acid) (PCA), were prepared by polycondensation. Amphiphilic PCA–DTT copolymers were prepared by grafting dithiothreitiol (DTT) into PCA by the Michael addition. PCA–DTT nanoparticles were self-assembled by additional water into a DMSO solution of PCA–DTT. The diameter and photoresponsivity of the PCA–DTT nanoparticles were influenced by the DB, and they increased with increasing the DB. Bovine serum albumin (BSA) as a model protein was successfully encapsulated into the PCA–DTT nanoparticles, and the release behavior of BSA was affected by the DB in PBS. These biodegradable and photoresponsive nanoparticles would be useful as functional carriers for drug delivery systems.

A novel series of biodegradable copolymers were synthesized by the thermal polycondensation of 3,4-dihydroxycinnamic acid (DHCA) and poly(ethylene glycol) (PEG). The copolymers were characterized by ¹H-NMR, Fourier transform infrared spectroscopy, and gel permeation chromatography. It was found that the incorporation of PEG reduced the glass-transition temperature (T_g) of the copolymers, and T_g decreased with increasing amount of PEG in the compositions. The fluorescence spectroscopy revealed that the homopolymer and copolymers of DHCA gave a higher fluorescence emission intensity than that of DHCA monomer, of which the strongest fluorescence emission peak occurred in the copolymers containing a small amount of PEG. X-ray diffraction spectra demonstrated that poly(3,4-dihydroxycinnamic acid) and copolymer were amorphous; this indicated the facile biodegradability of the copolymers. Furthermore, copolymer micelles formed by self-assembly were investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Photoreactive and degradable hyperbranched (HB) copolymers with various 3,4-dihydroxycinnamic acid (DHCA) compositions, poly(ε-caprolactone)-co-poly(3,4-dihydroxycinnamic acid) (PCL-co-PDHCA), were obtained by thermal melt-polycondensation of PCL and DHCA. The HB structures and the branching degree (BD) of the PCL-co-PDHCA copolymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (¹H NMR). The melting points (T_m) of the PCL-co-PDHCA copolymers changed depending on the PCL and DHCA composition by differential scanning calorimetry (DSC) measurements. Wide angle X-ray diffraction (WXRD) analysis showed semi-crystalline of the PCL and PCL-co-PDHCA polymers. The PCL-co-PDHCA copolymers showed good photoreactivities and fluorescent properties. Crosslinking of the cinnamoyl groups in the copolymers caused by UV irradiation affected the thermal stability and wettability slightly. Moreover, the hydrolysis experiments revealed that copolymers are facile degradable.

Monodispersed silver nanoparticles were immobilized onto the surface of poly(N-isopropylacrylamide) grafted poly(acrylonitrile/styrene) (PNIPAAm-g-PAN/PSt) microspheres by a one-step method using AgNO₃ as a silver source. This process was performed via the coordination interaction between Ag⁺ ions and amide groups on PNIPAAm-g-PAN/PSt microsphere surfaces with the reduction of the corresponding ions by ethanol taking place simultaneously. Fourier transform infrared (FTIR) spectroscopy and ultraviolet (UV)-visible spectra illustrated that the silver nanoparticles were successfully immobilized onto the PNIPAAm-g-PAN/PSt microspheres. The size and morphology of silvered microspheres were characterized by transmission electron microscopy (TEM). The weight percent of silver nanoparticles immobilized onto the microspheres was 12% based on the determination of thermogravimetric analysis (TGA). The antibacterial tests demonstrated that the as-prepared silvered microspheres showed activity against Gram-negative bacteria.

Poly(4-vinylpyridine) macromonomer (St-P4VP) with a styryl end group was synthesized by atom transfer radical polymerization (ATRP) of 4-vinylpyridine using p-(chloromethyl)styrene (CMSt) as functional initiator, CuCl as catalyst and tris[2-(dimethylamino)ethyl]amine (Me₆TREN) as ligand in 2-propanol. The structure of St-P4VP macromonomer was identified by proton nuclear magnetic resonance (¹H NMR). The result of gel permeation chromatography (GPC) illustrated that the number-average molecular weight of St-P4VP could be controlled by adjusting polymerization conditions. Poly(4-vinylpyridine) grafted polystyrene microspheres (P4VP-g-PSt) were then prepared by dispersion copolymerization of styrene with St-P4VP macromonomers. The effects of polymerization reaction parameters such as medium polarity, concentration of St-P4VP macromonomer and polymerization temperature on the sizes and size distribution of P4VP-g-PSt microspheres were investigated. The results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser light scattering (LLS) indicated that mono-dispersed P4VP-g-PSt microspheres with average diameters of 100–200 nm could be obtained when the molar ratio of St to St-P4VP was 0.25:100 in ethanol/water mixed solvents (V/V=80:20) at 60°C. Such kind of graft copolymer microspheres was expected to be applied to many fields such as drug delivery system and protein adsorption/separation system due to their particular structure.

Poly(tert-butyl methacrylate) macrointermediates (PtBMA-Br) with an end of bromine atom were synthesized by atom transfer radical polymerization using ethylbromopropionate as an initiator in bulk in the presence of N,N,N′,N′′,N′′-pentamethyl diethylenetriamine (PMDETA) as a single ligand. A new macromonomer (MAA- PtBMA) was successfully prepared via end-group nucleophilic substitution with methacrylic acid to attain a high efficiency of C=C incorporation. The molecular weights of MAA-PtBMA macromonomers were controllable from 5400 to 11000 g/mol, and the molecular weight distribution was narrow (≤1.20). Then, the PtBMA graft polystyrene (PtBMA-g-PSt) microspheres were prepared by dispersion copolymerization of MAA-PtBMA macromonomers with styrene using 2,2′-azobisisobutyronitrile as a free radical initiator in ethanol. The resulting PtBMA-g-PSt microspheres were regulated in diameter on a micron scale.