Amphiphilic Graft Polymers Research Articles

Synthesis and characterization of poly‐α,β‐[N‐(2‐hydroxyethyl)‐L‐aspartamide]‐g‐poly(L‐lactide) biodegradable copolymers as drug carriers

A series of biodegradable amphiphilic graft polymers were successfully synthesized by grafting poly(L-lactide) (PLLA) sequences onto a water-soluble polymer poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. We established the feasibility of preparing these novel graft polymers by the ring-opening polymerization initiated by the macroinitiator PHEA bearing hydroxyl groups without adding any catalyst. The successful grafting of PLLA sequences onto the PHEA backbone was verified by combined size exclusion chromatography (SEC) and multiangle laser light scattering (MALLS) analysis. The chemical structures of graft polymers were characterized by FTIR and (1)H NMR. The critical micelle concentration (CMC) of the graft polymer was determined by fluorescence probe technique using pyrene. By controlling the feed ratio of the macroinitiator to the monomer, graft polymers with different branch lengths can be obtained. Using the 3-(4,5 dimethylthiozol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay, the graft copolymer has been proved to have low cytotoxicity. Based on the amphiphilicity of the graft copolymers, nanoparticular drug delivery systems were prepared by the direct dissolution method and the dialysis method. The anticancer drug Tegafur was encapsulated into polymeric nanoparticles, and in vitro drug release behavior was investigated. Transmission electron microscopy (TEM) images demonstrate that these nanoparticles are regularly spherical in shape. The particle size and distribution of the nanoparticles were measured.

Synthesis, Characterization, and Degradation Behavior of Amphiphilic Poly-α,β-[N-(2-hydroxyethyl)-l-aspartamide]-g-poly(ε-caprolactone)

A series of biodegradable amphiphilic graft polymers were successfully synthesized by grafting poly(epsilon-caprolactone) (PCL) sequences onto a water-soluble poly-alpha,beta-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. The graft copolymers were prepared through the ring-opening polymerization of epsilon-caprolactone (CL) initiated by the macroinitiator PHEA with pendant hydroxyl groups without adding any catalyst. By controlling the feed ratio of the macroinitiator to the monomer, the copolymers with different branch lengths and properties can be obtained. The successful grafting of PCL sequences onto the PHEA backbone was verified by FTIR, 1H NMR, and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. The hydrolytic degradation and enzymatic degradation of these graft copolymers were investigated. The results show the hydrolytic degradation rate increases with increasing content of hydrophilic PHEA backbone. While the enzymatic degradation rate is affected by two competitive factors, the catalytic effect of Pseudomonas cepacia lipase on the degradation of PCL branches and the hydrophilicity which depends on the copolymer composition. In situ observation of the degradation under polarizing light microscope (PLM) demonstrates the different degradation rates of different regions in the polymer samples.

Synthesis and characterization of novel biodegradable amphiphilic graft polymers based on aliphatic polycarbonate

Synthesis and characterization of novel biodegradable amphiphilic graft polymers based on aliphatic polycarbonate

Polymer micelle-like aggregates of novel amphiphilic biodegradable poly(asparagine) grafted with poly(caprolactone)

Novel amphiphilic graft copolymers composed of poly(asparagine) (PAsn) as the hydrophilic backbone and poly(caprolactone) (PCL) as the hydrophobic segment were successfully synthesized by grafting PCL–HMDs to poly(succinimde). After tosylating PCL-diol with p-toluenesulfonylchloride (TsCl), tosylated poly(caprolactone) (PCL–OTs) was then reacted with hexamethylenediamine (HMD). The reaction of the amine terminated PCL with poly(succinimide) (PSI) and the following aminolysis resulted in poly(aspargine)- graft-poly(caprolactone) (PAsn- g-PCL). The degree of substitution (DS) and grafting reaction was confirmed by 13C NMR, FT-IR spectroscopy and elemental analysis. X-ray diffraction and DSC thermogram showed that the crystalline domain originated from PCL became apparent with an increase of DS. The amphiphilic comb-type graft polymer formed self-aggregates in aqueous solution when precipitated and dialysed against distilled water. Strong hydrophobic interaction of associated PCL grafts facilitated primary aggregate formation with DS, significantly reducing critical aggregation concentration and secondary aggregates also appeared in DLS measurements. Self-aggregates showed a bimodal size distribution originated from the self-aggregation and kinetically controlled particle aggregation, although the smaller primary aggregates was predominant. Spherical and dispersed aggregates of about 20 nm in diameter were observed by a transmission electron microscope.

Polyfunctional polyisobutenes as building blocks for amphiphilic graft polymers

AbstractPolyfunctional polyisobutenes (PIB) have been synthesized by cationic copolymerization of isobutene and chloromethylstyrene. Their potential applications with focus on their use as macroinitiators (MI) for oxazoline polymerization were discussed. The “grafting from” reaction led to tailor‐made graft copolymers with various backbones and adjustable graft arm length. Graft copolymers with hydrophobic PIB backbone and poly(2‐methyloxazoline) graft arms have unusual viscosity properties due to their amphiphilic character and show aggregate formation.

Preferential Solvent Absorption by Polymer Brushes from Immiscible Solvent Pairs

Hydrophilic, hydrophobic, and amphiphilic graft polymer brushes are synthesized by grafting polyacrylic acid and or polymethyl meth-acrylate onto gelatin granules crosslinked with glutaraldehyde. The ability of these brushes to selectively imbibe a solvent from immiscible pairs of solvents is demonstrated. The enhanced solvent mopping ability of the lipophilic and amphiphilic brushes from mixed solvent systems is interpreted through modified solvent interaction parameters.

Star‐shaped polymers by living cationic polymerization. VII. Amphiphilic graft polymers of vinyl ethers with hydroxyl groups: Synthesis and host–guest interaction

AbstractAmphiphilic graft polymers of vinyl ethers (VEs) (6) where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(alkyl vinyl ether) segment were prepared on the basis of living cationic polymerization, and their properties and functions were compared with the corresponding amphiphilic star‐shaped polymers. In toluene at −15°C, the HI/ZnI2‐initiated living block polymer 2 of an ester‐containing VE (CH2CHOCH2CH2OCOCH3) and isobutyl VE (IBVE) was terminated with the diethyl 2‐(vinyloxy)ethylmalonate anion [3; ΦC(COOEt)2CH2CH2OCH  CH2] (2/3 = 1/2 mole ratio) to give a macromonomer (4), H[CH2CH(OCH2CH2OCOCH3)] m‐[CH2CH(OiBu)]nC(COOEt)2CH2CH2OCH  CH2 (m = 5, n = 15; M̄n = 2600, M̄w/M̄n = 1.13, 1.10 vinyl groups/chain). Subsequently, 4 was homopolymerized with HI/ZnI2 in toluene at −15°C. In 3 h, 85% of 4 was consumed and a graft polymer (5) was obtained [M̄w = 15000, DPn (for 4) = 6]. The apparent M̄w (10,900) of 5 by size‐exclusion chromatography (SEC) is smaller than that by light scattering as well as that (18,300) by SEC of the corresponding linear polymer with the almost same molecular weight, indicating the formation of a multi‐branched structure. Hydrolysis of the pendant esters in 5 gave the amphiphilic graft polymer 6 where each branch consists of a hydrophilic polyalcohol and a hydrophobic poly(IBVE) segment. The graft polymer 6 was found to interact specifically with small organic molecules (guests) with polar functional groups, and 6 differed in solubility and host‐guest interaction from the corresponding star‐shaped polymer. © 1993 John Wiley & Sons, Inc.