RAFT Agents for Making Well-Defined Functionalized Polymers

Liz G. Williams¹, Ken Sullivan², John Tsanaktsidis¹

¹CSIRO Manufacturing, Ian Wark Laboratory, Bayview Avenue, Clayton, Victoria 3168, Australia, and, ²Boron Molecular INC, 2650-110 Discovery Drive, Raleigh, NC 27616 USA

RAFT Agents at Commercial Scale

The supply of low cost, high purity and effective Reversible addition−fragmentation chain-transfer (RAFT) Agents is the essential element in the industrial implementation of RAFT polymerization technology. While many RAFT Agents have been synthesized and utilized in polymerization reactions at laboratory scale, the availability of suitable low cost, low‑odour, high purity RAFT Agents at industrial scale is critical for commercial uptake.

Five novel RAFT agents (900152, 900161, 900150, 900157, 900158) have been added to the Sigma Aldrich RAFT Agent catalogue. These versatile, low to no-odour, low cost RAFT Agents are now available in gram to metric tonne quantities.

RAFT Agents – Selection Table

Selection of the RAFT Agent for the monomers and reaction conditions are crucial for the success of a RAFT polymerization experiment. The effectiveness of RAFT Agents is determined by the substituents R and Z. The RAFT Agents – Monomer Compatibility Table below provides an easy guide for selecting the optimal RAFT Agent from these five new RAFT Agents.

Aqueous and Organic Soluble RAFT Agents

900161 is an aqueous and organic soluble RAFT Agent, that provides excellent control of molecular weight, with narrow polydispersities (<1.1) for both the 2° (Styrenes, Acrylates, Acrylamindes) and the 3° (Methacrylates, Methacrylamides) More Activated Monomers (MAMs). It is recommended the use of 900161 for aqueous and emulsion polymerisations, and for flexibility of monomer choice from the MAM suite.

900152 has also been designed for both aqueous and organic solubility, and is the RAFT Agent of choice when considering polymerisation of the 2° MAM class. Very narrow polydispersities (<1.1) are achieved using this RAFT Agent.

The Pyrazole RAFT Agents

The pyrazole RAFT Agents reflect the need to access multifunctional polymers using a variety of electronically distinct monomer classes. These RAFT Agents are organic soluble, and offer no odour (no thiols), and greater end group stability, whilst also being amenable to end group removal.

900150 is the RAFT agent of choice for the homo-polymerisation, co-polymerisation and block co-polymerisation of the 2° More Activated Monomers (MAMs) and the 2° Less Activated Monomers (LAMs – vinyl esters, vinyl amides). When used for a homo-polymerisation or block co-polymerisation, a short block containing the 2° MAMs is required first, to enable the controlled polymerisation of the 2° LAMs.

900157 is described as a ‘versatile RAFT Agent’, able to polymerise all three monomer classes. This RAFT Agent provides excellent control of molecular weight and narrow polydispersities for the 2° MAMs (<1.1) and moderate polydispersities for the 2° LAMs (1.1 - 1.3). For the homo-polymerisation or block polymerisation of LAMs, a short block containing the 2° MAMs is required first, to enable the controlled polymerisation of the 2° LAMs. 900157 is able to homo-polymerise, co-polymerise and block co-polymerise the 3° MAMs, however, whilst good control of molecular weight is achieved, a broader polydispersity (>1.3) is seen with this RAFT Agent. If polydispersity is less critical for your applications, 900157 is recommended as a versatile RAFT Agent, allowing polymerisation of the three monomer classes without the need for ‘switching’.

900158 is also a ‘versatile RAFT Agent’, able to polymerise all three monomer classes. If polydispersity is important for your applications, this RAFT Agent is recommended. Excellent control of molecular weight, and narrow dispersities (<1.1) are achieved for the 2° MAMs, whilst moderate dispersities (1.1 – 1.3) are achieved for the 3° MAMs and 2° LAMs, thus enabling the preparation of controlled, multifunctional (block) co-polymers on commercial scale, using a wide range of electronically differentiated monomers. For the homo-polymerisation or block polymerisation of LAMs, a short block containing the 2° MAMs is required first, to enable the controlled polymerisation of the 2° LAMs.

Summary

The RAFT Agents featured in the Selection Table are now available for both commercial and R&D applications. These versatile, low to no-odour, low cost RAFT Agents are available in gram to metric tonne quantities. The RAFT Agents – Selection Table is designed to assist the RAFT Technology user to choose the best RAFT Agent to ensure the best polymerization outcome.