RAFT Inverse Miniemulsion Polymerization of Acrylamide

RAFT inverse miniemulsion polymerization is demonstrated for the first time as an alternate way to synthesize hydrophilic polymer latexes. The kinetic behavior of inverse RAFT miniemulsion polymerization of acrylamide is similar to that observed in aqueous RAFT solution polymerization. A water‐soluble initiator provides better control than a lipophilic initiator in inverse RAFT miniemulsion polymerization under the conditions used here.

     

Preparation of Highly Transparent and Thermally Stable Films of α‐Cyclodextrin/Polymer Inclusion Complexes

Films of an α‐cyclodextrin/poly(ε‐caprolactone) inclusion complex have been successfully prepared and show high transparency and heat resistance in comparison to the pure polymer film. The physical properties, such as transparency, mechanical properties, and thermal stability, of the α‐CD‐PCL‐IC films are found to depend on the α‐cyclodextrin‐to‐polymer stoichiometry.

     

Step‐Growth Radical Addition‐Coupling Polymerization (RACP) for Synthesis of Alternating Copolymers

We report a new type of step‐growth radical addition‐coupling polymerization (RACP) involving consecutive addition of carbon‐centered radical derived from α,α′‐dibromo dibasic ester to NO double bond of C‐nitroso compound followed by cross‐coupling of carbon‐centered radical and in situ formed nitroxyl radical, which produces alternating copolymers with high molecular weight and unimodal molecular weight distribution from saturated and unsaturated monomers.

     

Kinetic Modeling as a Tool to Understand and Improve the Nitroxide Mediated Polymerization of Styrene

Kinetic modeling is used to obtain insight in the complex interplay between reaction rates and obtained polymer properties in the SG1 and the TEMPO mediated bulk polymerization of styrene at 396 K. The increase of the viscosity during NMP is accounted for. At higher targeted chain lengths, chain transfer to dimer and transfer from nitroxide to dimer are shown to cause the experimentally observed reduced control over the average polymer properties and to result in a clear fronting of the polymer chain length distribution. The potential of kinetic modeling to design tailor‐made synthesis strategies is illustrated. Simulations indicate that careful control of the polymerization conditions allows to obtain an important improvement of the polymer properties. The approach is also applicable for NMP mediated by other alkoxyamines/nitroxides and allows to expand the application range of NMP for styrene polymerization in particular to synthesize complex polymer architectures by assembly of functionalized polymers.

     

Controlled Alternating Copolymerization of (Meth)acrylates and Vinyl Ethers by Using Organoheteroatom‐Mediated Living Radical Polymerization

Alternating copolymers comprised of (meth)acrylates and vinyl ethers with controlled molecular weights and polydispersities were synthesized for the first time by living radical polymerization using organotellurium, stibine, and bismuthine chain transfer agents. Combining living alternating copolymerization and living radical or living cationic polymerization afforded hitherto unavailable block copolymers with controlled macromolecular structures.

     

Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self‐Degraded Template

Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl₃ and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.

TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.     

Poly(2,5‐thienylene vinylene) in Nano Shapes by CVD Polymerization

Poly(2,5‐thienylene vinylene) (PTV), an insoluble conjugated polymer, can be readily prepared in various shapes of different nanodimensions by the chemical vapor deposition polymerization of 2,5‐bis(chloromethyl)thiophene. The bischloromethyl monomer in the vapor phase is activated at 600 °C. The activated monomer vapor is deposited at room temperature on the surface of various substrates to prepare polymeric films, fibers, tubes etc., which are then thermally converted into PTV. PTV thin films can be carbonized thermally to produce graphitic compositions that contain sulfur atoms. Electrical conductivities of FeCl‐doped PTV and carbonized films are reported.

     

Parametric Analysis of the Intermediate Concentration in a RAFT Polymerization and its Influence upon the Polymerization Kinetics

Summary: A kinetic analysis of living/controlled radical polymerizations in bulk mediated by RAFT is presented. The main objective is to show how the kinetics of the RAFT process and, in particular, of the RAFT intermediate radical is affecting the overall polymerization rate. Namely, three different cases are analyzed: (i) slow fragmentation of the RAFT intermediate; (ii) cross‐termination of the RAFT intermediate with other radicals; and (iii) slow re‐initiation of the RAFT agent leaving group. Simplified analytical formulas are derived for the time‐dependent concentrations of the involved species as well as for conversion. They are supported by numerical simulations and are qualitatively compared to literature experimental findings. Criteria are also given to judge the influence of the RAFT reaction kinetic rate constants on the different phenomena observed experimentally in RAFT polymerization, namely inhibition and retardation. Since these criteria are given by using non‐dimensional groups, they can be readily applied to a broad spectrum of experimental conditions.

Logarithmic non‐dimensional concentration for the radicals (r) and intermediate radicals (q) versus the non‐dimensional polymerization time ( ).     

Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) is a robust method for the preparation of well‐defined (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization.

Formation of polymer brushes by ATRP.     

Combining RAFT Radical Polymerization and Click/Highly Efficient Coupling Chemistries: A Powerful Strategy for the Preparation of Novel Materials

This paper highlights the powerful combination of reversible addition–fragmentation chain transfer (RAFT) radical polymerization and various click/coupling chemistries. This is not an exhaustive review but rather an overview demonstrating the impressive possibilities that the “marriage” of these two synthetic approaches offers in modern macromolecular design and synthesis.

     

A Novel Approach to Population Balance Modeling of Reactive Polymer Modification Leading to Branching

The mathematical treatment of polymer modification systems, described by population balances containing convolution is discussed. The two‐dimensional case (molecular weight vs. number of branch points) was considered by utilizing approximations of distributions, expanding them in terms of Gaussian basis functions. Three branching reactions were addressed: chain backbone to chain end point coupling; three‐functional coupling of chain ends; and crosslinking. The results were compared to those of Monte Carlo (MC) simulations. Good agreement was observed, although the quality of a distribution as generated by the numerical approach is much better in view of the strong scatter in the MC data.

     

Formation of Vesicular Morphologies via Polymerization Induced Self‐Assembly and Re‐Organization

A facile and feasible strategy for the preparation of vesicular morphologies has been developed using reversible addition–fragmentation chain transfer (RAFT) polymerization. The polymerization of styrene has been performed in a selected solvent, methanol, using S‐1‐dodecyl‐S‐(α,α′‐dimethyl‐α″‐acetic acid)trithiocarbonate (TC)‐terminated poly(4‐vinylpyridine) as chain transfer agent and stabilizer. Various morphologies including spherical vesicles, nanotubes, and compound vesicles with different shapes are obtained by changing the feed ratios and reaction conditions. The final nanostructural materials are formed through formation of the block copolymers, self‐assembly, and re‐organization of the morphology in a one‐pot polymerization. The latter two are induced by the propagation of PS blocks. The preparation of nanostructural materials can be performed at a concentration higher than 0.5 g · mL⁻¹, thus this method offers a practical approach to prepare nanostructural materials on a large scale.

     

Defined Poly[styrene‐block‐(ferrocenylmethyl methacrylate)] Diblock Copolymers via Living Anionic Polymerization

Ferrocenylmethyl methacrylate (FMMA) is one of the very few metallocene‐based monomers that are promising candidates for truly living anionic polymerization. Nevertheless, FMMA homopolymers with a narrow polydispersity, or block copolymerization studies that result in satisfying blocking efficiencies, are unknown so far. Here we describe a procedure that leads to highly regular FMMA‐based polymers for the first time, characterized by polydispersity indices (PDI) of less that 1.05 and very high blocking efficiencies (>95%) in sequential copolymerization with styrene. Some of the obtained poly[styrene‐block‐(ferrocenylmethyl methacrylate)]s show unusual microphase morphologies, presumably the consequence of high T_gs causing ‘frustrated’ non‐equilibrium states.

     

Crystallization of Poly(ε‐caprolactone)/Poly(vinyl chloride) Miscible Blends Under Strain: The Role of Molecular Weight

Summary: The effect of poly(ε‐caprolactone) (PCL) molecular weight on the orientation of crystalline PCL in miscible poly(ε‐caprolactone)/poly(vinyl chloride) (PCL/PVC) blends, melt crystallized under strain, has been studied by a combination of wide angle X‐ray diffraction (WAXD) and small angle X‐ray scattering (SAXS) studies. An unusual crystal orientation with the b‐axis parallel to the stretching direction was observed in miscible PCL/PVC blends with PCL of high molecular weight (>21 000). SAXS showed the presence of nanosize confined PCL in the PCL/PVC blends, which could be preserved at temperatures higher than the T_m of PCL but lower than the T_g of PVC. A mechanism based on the confinement of PCL crystal growth was proposed, which can explain the formation of b‐axis orientation in PCL/PVC blends crystallized under strain.

SAXS pattern of stretched PCL/PVC blend after annealing at 90 °C for 5 min.     

Application of Poly(3‐hexylthiophene) Functionalized with an Anchoring Group in Dye‐sensitized Solar Cells

A series of three poly(3‐hexylthiophene) functionalized either with a cyanoacetic acid (CA) or a rhodanine‐3‐acetic acid anchoring groups were synthesized and characterized. The TiO₂ based dye‐sensitized solar cells have been fabricated and performances were tested. We show that shorter chain length (15 thiophene units) linked to CA binding group gives good performances as J_sc, V_oc, FF and η(%) were 6.93(mA · cm⁻²), 0.65(V), 0.67 and 3.02%, respectively. A maximum IPCE of ≈50% at 500 nm was recorded with a liquid electrolyte, under AM 1.5 simulated solar irradiance.