Elizabeth A. Rainbolt

Recent developments in micellar drug carriers featuring substituted poly(ε-caprolactone)s

In the field of drug delivery, synthetic polymers have been widely explored due to their range of properties and functions achievable by tuning their structures. Poly(e-caprolactone)s in particular have established themselves as excellent candidates for biomedical applications because of their biocompatibility, biodegradability, and synthetic versatility. In this review, applications of functional poly(e-caprolactone)s in drug delivery systems are highlighted. Recent studies regarding the encapsulation or direct conjugation of drugs, bioactive molecules and moieties for targeting are discussed. Also considered are advances in amphiphilic polymers with functional poly(e-caprolactone)s that exhibit stimuli-responsive behavior: pH-, thermo-, photo-, and reduction-sensitive. Ongoing research and development of functional poly(e-caprolactone)s continues to expand their potential for use in micellar drug delivery systems.

Benzodifuran and benzodithiophene donor–acceptor polymers for bulk heterojunction solar cells

Four new donor–acceptor copolymers were synthesized by using benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-b:4,5-b′]difuran as donors and thieno[3,4-b]thiophene was used as the acceptor building block. A systematic study was performed to determine the influence of the combinations of different heteroatoms in the donor–acceptor copolymer. In bulk heterojunction solar cells, the polymer with all furan building blocks in the electron donating units, poly[(4,8-bis(5-dodecyl-2-furanyl)benzo[1,2-b:4,5-b′]difuran-2-yl)-alt-(2-ethyl-1-(3-fluorothieno[3,4-b]thiophen-2-yl)-1-hexanone)] (P4) (Mn = 66.7 kDa), achieved the highest power conversion efficiency of 5.23%.

A semiconducting liquid crystalline block copolymer containing regioregular poly(3-hexylthiophene) and nematic poly(n-hexyl isocyanate) and its application in bulk heterojunction solar cells

A liquid crystalline diblock copolymer containing regioregular poly(3-hexylthiophene) (P3HT) and poly(n-hexyl isocyanate) (PHIC) was synthesized by the combination of Grignard metathesis polymerization (GRIM) and titanium mediated coordination polymerization methods. The poly(3-hexylthiophene)-b-poly(n-hexyl isocyanate) (P3HT-b-PHIC) diblock copolymer used in this study contained ∼10 mol% of P3HT and ∼90 mol% of PHIC. The diblock copolymer displayed solvatochromism in THF–water and THF–methanol mixtures. The field-effect mobilities of the synthesized block copolymer were measured in bottom gate-bottom contact organic field-effect transistors (OFETs). The surface morphology of the polymer thin film was investigated in the channel region of the OFET devices by tapping mode atomic force microscopy (TMAFM). The diblock copolymer displayed nanostructured morphology in thin film and had good mobility despite the low content of the semiconducting P3HT block. The diblock copolymer was also used as an additive to improve the performance of P3HT/PCBM bulk heterojunction (BHJ) solar cells. Liquid crystalline characteristics of the diblock copolymer were examined by cross-polarizing microscopy and X-ray diffraction.

Towards smart polymeric drug carriers: Self-assembling γ-substituted polycaprolactones with highly tunable thermoresponsive behavior

Synthesis and ring opening polymerization of a new γ-substituted ε-caprolactone monomer, γ-(2-methoxyethoxy)-ε-caprolactone is reported. Amphiphilic diblock copolymers comprised of poly[γ-(2-methoxyethoxy)-ε-caprolactone] and thermosensitive poly{γ-2-[2-(2-methoxyethoxy)ethoxy]ethoxy-ε-caprolactone} as the hydrophobic and hydrophilic blocks, respectively, were prepared. The copolymers exhibited fully biodegradable backbones and highly tunable thermoresponsive behavior in the range of 31-43 °C. Additionally, the copolymers were shown to self-assemble in aqueous media above their respective critical micelle concentrations, on the order of 10-2 g L-1. Due to their thermosensitive, self-assembling, and biodegradable properties, these copolymers demonstrate potential for the use in polymeric micellar drug delivery systems.

Benzodithiophene homopolymers synthesized by Grignard metathesis (GRIM) and Stille coupling polymerizations

Poly{4,8-bis(95-dodecylthiophene-2-yl)benzo[1,2-b:4,5-b′]dithiophene} has been synthesized by both Grignard metathesis (P1) and Stille coupling polymerizations (P2). Polymers P1 and P2 were characterized and their optoelectronic properties, charge carrier mobilities, and photovoltaic properties were compared. The field-effect mobilities of the polymers were measured on both untreated and heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane (FS) treated organic field effect transistor (OFET) devices. The polymers were also evaluated in bulk heterojunction (BHJ) solar cells with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor.

Synthesis and characterization of a polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) triblock copolymer

A polyisoprene-b-polystyrene-b-poly(3-hexylthiophene) triblock copolymer was synthesized by anionic coupling of living polyisoprene-b-polystyryl lithium with allyl-terminated poly(3-hexylthiophene). The triblock copolymer retained the opto-electronic properties and morphology found in the poly(3-hexylthiophene) homopolymer despite the insulating polyisoprene and polystyrene blocks, making it potentially useful as an elastomeric semiconducting material.

Nitrogen containing graphene-like structures from pyrolysis of pyrimidine polymers for polymer/graphene hybrid field effect transistors

Nitrogen containing graphene like structures were obtained by the pyrolysis of two pyrimidine polymers at 600 °C. Pyrimidine polymers were prepared by the base catalyzed aldol condensation reactions between 2-decyloxy-4,6-dimethylpyrimidine and two aromatic dialdehydes. Pyrolyzed products were shown to have a graphitic structure by Raman spectroscopy, scanning electron microscopy, and powder X-ray diffraction studies. The presence of nitrogen in the graphitic structures was proved by elemental analysis and energy dispersive X-ray analysis experiments. Fluorescence quenching experiments with poly(3-hexylthiophene) (P3HT) showed that the resultant graphitic material can act as an acceptor. These materials were tested in P3HT/graphene hybrid field effect transistors which exhibited higher mobilities and comparable on/off ratios compared to P3HT only devices.