Synthesis and characterization of novel hydrophobically modified polybetaines as pour point depressants

A review of polyampholytic ion scavengers for toxic metal ion removal from aqueous systems

Pollution by heavy metal ions in aqueous systems gained researchers attention gradually. Toxic metal ions were always present in the environment and the living organisms could get used to specific concentrations of contaminants with given time, however, sudden concentration rise we are observing can make it impossible for the living organisms to adapt. Many ion removal technologies were developed and optimised over the years to cope with this problem, including chemical precipitation, adsorption, membrane filtration and ion-exchange. Adsorption and ion exchange are processes that employ certain materials, that can be collectively named ion scavengers, to remove ions from aqueous solutions. Some of the scavenger materials are still barely studied, in particular polyampholytes - polymeric zwitterionic materials. This review showcases papers published on toxic metal ion removal by polyampholytes, both commercial and experimental, over last two decades. Many recent publications show promising properties of experimental materials that match or even outperform commercial scavengers. This review was prepared to encourage other researchers to investigate this broad and still not well-studied class of materials especially in context of their ion-scavenging properties. Polyamphytes which may be especially worth the attention and further research have been highlighted as literature studies show that the most unexplored materials in the class of polyamphytes are those containing aminomethylphosphonate, aminomethylsulfonate or hypophosphorous acid group.

Reversible Addition?Fragmentation Chain-Transfer Polymerization of Amphiphilic Polycarboxybetaines and Their Molecular Interactions

In this work, we report the first molecular weight-controlled amphiphilic polybetaine synthesis using various hydrocarbons via reversible addition?fragmentation chain-transfer (RAFT) polymerization. The experimental separation of the alkyl aminocrotonate tautomers, which has been the subject of debate, was completed for the first time. The enamine form of these tautomers was further used as a monomer for the RAFT polymerization of amphiphilic polycarboxybetaines. Self-assembly of the amphiphilic polycarboxybetaines showed micelle structures from spherical, rod-like to fractal in the aqueous media due to the competition between both electrostatic and hydrophobic forces. Hydrophobically dominant interactions among amphiphilic polycarboxybetaines and long-chain hydrocarbon alkane molecules were investigated to understand long-chain hydrocarbon alkane crystallization using alkane crystal deposition and viscosity experiments. Strong hydrophobic forces between poly(hexadecyl-grafted aminocrotonate?methacrylic acid) and long-chain hydrocarbon alkane molecules changed the surface properties of the long-chain hydrocarbon alkane nucleus and inhibited the growth of paraffin crystals.

Hydrophobically Modified Polycarboxybetaine: From Living Radical Polymerization to Self-Assembly

Polybetaines have received widespread attention due to their smart response properties and structures which resemble biological polymers like peptides and DNA. However, few studies have focused on the controlled synthesis and self-assembly of hydrophobically modified polybetaines due to the difficulty of synthesizing these materials. We report the first molecular weight-controlled synthesis of hydrophobically modified polycarboxybetaines (HMPCB). Poly(dodecyl grafted aminocrotonate -methacrylic acid) (P(DACRO-MAA)) was synthesized via the reversible addition-fragmentation chain-transfer (RAFT) polymerization approach. The two different tautomers of the monomer were also successfully identified and separated via thin layer chromatography (TLC) and column chromatography, making it possible to obtain pure polycarboxybetaine via RAFT synthesis. Both the successfully separated enamine form of the monomer and the resulting polycarboxybetaine were confirmed via FTIR and NMR. The polycarboxybetaine was found to have a low polydispersity (PDI) of 1.214, and its molecular weight was determined as 70590 g/mol via gel permeation chromatography (GPC) measurements. Spherical, rodlike, and fractal assembled structures for the P(DACRO-MAA) were observed with pH change using TEM, zeta sizer, and dynamic light scattering (DLS). The unique self-assembled structures of HMPCB synthesized via RAFT provide an opportunity to understand fundamental polymer science and can be engineered for broad applications.

Polyampholytic graft copolymers based on polydehydroalanine (PDha) – synthesis, solution behavior and application as dispersants for carbon nanotubes

We herein introduce a versatile platform of graft copolymers featuring a polyampholytic backbone and side chains of varying length and polarity using post-polymerization modification of polydehydroalanine (PDha).

Adsorption of Polymeric Additives Based on Vinyl Acetate Copolymers as Wax Dispersant and Its Relevance to Polymer Crystallization Mechanisms

The present work has main target to study the effect of additives molecular weight and composition on the flow characteristics of wax crude oil at low temperature below pour point temperature. In this respect, maleic anhydride ester-co-vinyl acetate copolymers with varied monomers feed ratios and different alkyl ester lengths, namely, dodecyl, stearyl, and behenyl alkyl chains, were prepared. These polymeric materials were characterized by FTIR,1HNMR, and GPC. The performance of these additives as pour point depressants and flow improver for Egyptian waxy crude oil was evaluated through measurements of pour point and rheological parameters (viscosity and yield stress). It was observed that stearyl maleate-vinyl acetate copolymer with 1 : 2 feed ratio shows the best efficiency as pour point depressant even at low concentration while octadecyl maleate-vinyl acetate copolymers with 2 : 1 feed ratio are effective as flow improver.