scholarly journals Effective End-Group Modification of Star-Shaped PNVCL from Xanthate to Trithiocarbonate Avoiding Chemical Crosslinking

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3677
Author(s):  
Norma A. Cortez-Lemus ◽  
Eduardo Hermosillo-Ochoa ◽  
Ángel Licea-Claverie
Keyword(s):  
Raft Polymerization ◽  
Benzyl Bromide ◽  
Star Polymers ◽  
Solution Concentration ◽  
Hydrodynamic Diameter ◽  
Reversible Addition ◽  
Yellow Color ◽  
Group Modification ◽  
End Group Modification ◽  
Responsive Behavior

In this study, six-arm star-shaped poly(N-vinylcaprolactam) (PNVCL) polymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization were subjected to aminolysis reaction using hexylamine. Chemically crosslinked gels or highly end-functionalized star polymers can be obtained depending mainly on the type of solvent used during the transformation of the RAFT functional group. An increase in the viscosity of the solution was observed when the aminolysis was carried out in THF. In contrast, when the reaction was conducted in dichloromethane, chain-end thiol (PNVCL)6 star polymers could be obtained. Moreover, when purified (PNVCL-SH)6 star polymers are in contact with THF, the gelation occurs in just a few minutes, with an obvious increase in viscosity, to form physical gels that become chemically crosslinked gels after 12 h. Interestingly, when purified (PNVCL-SH)6 star polymers were stirred in distilled water, even at high aqueous solution concentration (40 mg/mL), there was no increase in the viscosity or gelation, and no evident gels were observed. The analysis of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) did not detect quantifiable change even after 4 days of stirring in water. On the other hand, the thiol groups in the (PNVCL-SH)6 star polymers were easily transformed into trithiocarbonate groups by addition of CS2 followed by benzyl bromide as demonstrated by UV-Vis spectroscopical analysis and GPC. After the modification, the (PNVCL)6 star polymers exhibit an intense yellow color typical of the absorption band of trithiocarbonate group at 308 nm. To further demonstrate the highly effective new trithiocarbonate end-functionality, the PNVCL polymers were successfully chain extended with N-isopropylacrylamide (NIPAM) to form six-arm star-shaped PNIPAM-b-PNVCL block copolymers. Moreover, the terminal thiol end-functionality in the (PNVCL-SH)6 star polymers was linked via disulfide bond formation to l-cysteine to further demonstrate its reactivity. Zeta potential analysis shows the pH-responsive behavior of these star polymers due to l-cysteine end-functionalization. By this using methodology and properly selecting the solvent, various environment-sensitive star polymers with different end-groups could be easily accessible.

RAFT Polymer End-Group Modification and Chain Coupling/Conjugation Via Disulfide Bonds

2009 ◽  
Vol 62 (8) ◽  
pp. 830 ◽  
Author(s):  
Cyrille Boyer ◽  
Jingquan Liu ◽  
Volga Bulmus ◽  
Thomas P. Davis
Keyword(s):  
Disulfide Bonds ◽  
Diblock Copolymers ◽  
Raft Polymerization ◽  
Gel Permeation Chromatography ◽  
Reversible Addition ◽  
Group Modification ◽  
End Groups ◽  
End Group Modification ◽  
High Yields ◽  
End Group

End-group modification of polymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization was accomplished by the conversion of trithiocarbonate or dithioester end-groups into a pyridyl disulfide (PDS) functionality. Several different polymers, such as poly(methyl methacrylate), polystyrene, poly(oligoethylene glycol-acrylate), poly(hydroxypropylacrylamide), and poly(N-isopropylacrylamide) were prepared by RAFT polymerization, and subjected to aminolysis in the presence of 2,2′-dithiodipyridine to yield thiol-terminated polymers with yields in the range 65–90% dependent on the polymer structure. Furthermore, this PDS end-group was utilized to generate higher-order architectures, such as diblock copolymers with high yields and selectively. In addition, the PDS end-groups were used for the bioconjugation of different biomolecules, such as oligonucleotides, carbohydrates, and peptides. The successful modification of well-defined polymers was confirmed by a combination of UV-vis, NMR spectroscopy, and gel permeation chromatography.

Synthesis of Star Polymers using RAFT Polymerization: What is Possible?

2006 ◽  
Vol 59 (10) ◽  
pp. 719 ◽  
Author(s):  
Christopher Barner-Kowollik ◽  
Thomas P. Davis ◽  
Martina H. Stenzel
Keyword(s):  
Raft Polymerization ◽  
Star Polymers ◽  
Vinyl Pyrrolidone ◽  
Side Reactions ◽  
Radical Concentration ◽  
Reversible Addition ◽  
Polymer Architectures ◽  
Raft Agent ◽  
Poly Vinyl Pyrrolidone ◽  
Careful Design

Various pathways to generate star polymers using reversible addition–fragmentation transfer (RAFT) are discussed. Similar to other polymerization techniques, star polymers can be generated using arm-first and core-first approaches. Unique to the RAFT process is the subdivision of the core-first approach into the R-group and Z-group approaches, depending on the attachment of the RAFT agent to the multifunctional core. The mechanism of the R- and Z-group approaches are discussed in detail and it is shown that both techniques have to overcome difficulties arising from termination reactions. Termination reactions were found to broaden the molecular weight. However, these side reactions can be limited by careful design of the synthesis. Considerations include RAFT and radical concentration, number of arms, type of RAFT agent and monomer. Despite obvious challenges, the RAFT process is highly versatile, allowing the synthesis of novel polymer architectures such as poly(vinyl acetate) and poly(vinyl pyrrolidone) star polymers.

Doubly-responsive hyperbranched polymers and core-crosslinked star polymers with tunable reversibility

2015 ◽  
Vol 6 (45) ◽  
pp. 7871-7880 ◽  
Author(s):  
Sunirmal Pal ◽  
Megan R. Hill ◽  
Brent S. Sumerlin
Keyword(s):  
Chain Transfer ◽  
Raft Polymerization ◽  
Star Polymers ◽  
Hyperbranched Polymers ◽  
Reversible Addition ◽  
Redox Responsive

Thermo- and redox-responsive hyperbranched copolymers were prepared by statistical copolymerization of N-isopropylacrylamide (NIPAM) and N,N′-bis(acryloyl)cystamine (BAC) by reversible addition–fragmentation chain transfer (RAFT) polymerization.

scholarly journals Living Radical Polymerization by the RAFT Process

2005 ◽  
Vol 58 (6) ◽  
pp. 379 ◽  
Author(s):  
Graeme Moad ◽  
Ezio Rizzardo ◽  
San H. Thang
Keyword(s):  
Radical Polymerization ◽  
Polymer Brushes ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Star Polymers ◽  
Living Radical Polymerization ◽  
Factors Influencing ◽  
Reversible Addition ◽  
Complex Architectures

This paper presents a review of living radical polymerization achieved with thiocarbonylthio compounds [ZC(=S)SR] by a mechanism of reversible addition–fragmentation chain transfer (RAFT). Since we first introduced the technique in 1998, the number of papers and patents on the RAFT process has increased exponentially as the technique has proved to be one of the most versatile for the provision of polymers of well defined architecture. The factors influencing the effectiveness of RAFT agents and outcome of RAFT polymerization are detailed. With this insight, guidelines are presented on how to conduct RAFT and choose RAFT agents to achieve particular structures. A survey is provided of the current scope and applications of the RAFT process in the synthesis of well defined homo-, gradient, diblock, triblock, and star polymers, as well as more complex architectures including microgels and polymer brushes.

Synthesis of siRNA Polyplexes Adopting a Combination of RAFT Polymerization and Thiol-ene Chemistry

2009 ◽  
Vol 62 (10) ◽  
pp. 1344 ◽  
Author(s):  
David Valade ◽  
Cyrille Boyer ◽  
Thomas P. Davis ◽  
Volga Bulmus
Keyword(s):  
Block Copolymers ◽  
High Efficiency ◽  
Raft Polymerization ◽  
Hydrodynamic Diameter ◽  
Small Interfering Rnas ◽  
Buffer Solution ◽  
Polyelectrolyte Complexes ◽  
Reversible Addition ◽  
Hydroxypropyl Methacrylamide ◽  
Cationic Copolymers

Block copolymers of allyl methacrylate and N-(2-hydroxypropyl)methacrylamide (HPMA) with different block lengths have been synthesized by reversible addition–fragmentation chain transfer polymerization. Allyl groups were modified with cysteamine, via a thiol-ene photoreaction, with a high efficiency (~100%) as evidenced by NMR spectroscopy, yielding cationic copolymers of HPMA. Polyelectrolyte complexes of small interfering RNAs (siRNA) and the cationic block copolymers were then formed at an N/P ratio between 1 and 4 depending on the block length of the copolymers. Increasing the length of the hydrophilic block was found to decrease the efficiency of siRNA complexation. The hydrodynamic diameter of the polyplexes in 130 mM buffer solution was less than 100 nm.

scholarly journals Fabrication of Polymer Micelles with Zwitterionic Shell and Biodegradable Core for Reductively Responsive Release of Doxorubicin

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1019 ◽  
Author(s):  
Junting Jiang ◽  
Junbo Li ◽  
Biyu Zhou ◽  
Chaohuang Niu ◽  
Wendi Wang ◽  
...  
Keyword(s):  
Drug Release ◽  
Disulfide Bonds ◽  
High Stability ◽  
Polymeric Micelles ◽  
Raft Polymerization ◽  
Drug Efficacy ◽  
Low Protein ◽  
Self Assembling ◽  
Group Modification ◽  
End Group Modification

To achieve a high stability in physiological environment and rapid intracellular drug release, a biodegradable zwitterionic triblock copolymer with a disulfide-linked poly-ε-caprolactone and polycarboxybetaine methacrylate (PCBMA-SS-PCL-SS-PCBMA) was prepared for micellar carrier to delivery doxorubicin (DOX) into tumor cells. PCBMA-SS-PCL-SS-PCBMA was obtained by following steps: i) introducing disulfide bonds through end-group modification of PCL diol with cystamine dihydrochloride; ii) preparing PCL-RAFT macromolecular chain transfer agent by EDC/NHS chemistry; iii) RAFT polymerization of zwitterionic monomer. Self-assembling from PCBMA-SS-PCL-SS-PCBMA, polymeric micelles had many advantages, such as ultra-low protein absorption in serum and obvious reduction-responsiveness in the presence of DTT. Furthermore, DOX-loaded micelles exhibited high stability upon centrifugation and lyophilization, a fast intracellular drug release and enhanced drug efficacy due to GSH-triggered PCBMA shell shedding and micellar reassembling. Thus, the polymeric micelles integrated several functions and properties could be prospectively utilized as valuable nanocarriers in cancer chemotherapeutics.

Dendrimers as Scaffolds for Reversible Addition Fragmentation Chain Transfer (RAFT) Agents: a Route to Star-Shaped Block Copolymers

2005 ◽  
Vol 58 (6) ◽  
pp. 483 ◽  
Author(s):  
Xiaojuan Hao ◽  
Eva Malmström ◽  
Thomas P. Davis ◽  
Martina H. Stenzel ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Butyl Acrylate ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Star Polymers ◽  
Size Exclusion ◽  
Chain Extension ◽  
Reversible Addition ◽  
Star Block Copolymers

Star-shaped block copolymers of styrene and n-butyl acrylate having three, six, and twelve pendent arms were successfully synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization. Dendritic cores (based on 1,1,1-trimethylolpropane) of generation 0, 1, and 2 have been functionalized with 3-benzylsulfanylthiocarbonylsulfanylpropionic ester groups and have subsequently been employed to mediate the polymerization of styrene and n-butyl acrylate to generate macro-star-RAFT agents as starting materials for chain extension. The chain extension of the macro-star-RAFT agents with either styrene or n-butyl acrylate by bulk free radical polymerization at 60°C gives narrowly distributed polymer (final polydispersities close to 1.2) increasing linearly in molecular weight with increasing monomer-to-polymer conversion. However, with an increasing number of arms (i.e., when going from three- to twelve-armed star polymers), the chain extension becomes significantly less efficient. The molecular weight of the generated block copolymers was assessed using 1H NMR spectroscopy as well as size exclusion chromatography calibrated with linear polystyrene standards. The hydrodynamic radius, Rh, of the star block copolymers as well as the precursor star polymers was determined in tetrahydrofuran by dynamic light scattering (90°) at 25°C. Interestingly, the observed Rh–Mn relationships indicate a stronger dependence of Rh on Mn for poly(butyl acrylate) stars than for the corresponding styrene polymers. Rh increases significantly when the macro-star-RAFT agent is chain extended with either styrene or n-butyl acrylate.

Sign in / Sign up

Export Citation Format

Share Document