Dynamic pivot column list always with trailing whitespace

I have a problem creating a dynamic pivot table in SQL Server 2012.

My main table consists of timestamp,node_id,value columns:

I have another table t_node with nodename (NVARCHAR(400)) for each node_id.

I want to have a pivot table with

and so on.

I created a dynamic list first with all nodenames like HERE:

DECLARE @cols VARCHAR(MAX) SELECT @cols = isnull(@cols + ',', '') + '[' + nodename + ']' FROM [MyDB].[DBSpace01].t_node ORDER BY nodename 

When I print this @cols, I always get trailing whitespaces at the end of each entry - like this:

[nodename1 ], [nodename2 ], [nodename3 ] 

This then leads to errors when pivoting with this list because it results in an error:

'nodename1.' is an invalid name because it contains a NULL character or an invalid Unicode character.

I tried RTRIM and REPLACE and everything, but the list is either empty or has the whitespaces in the end. I also tried to have it with QUOTENAMES, but then the list is empty.

I do not understand enough of SQL Server to understand what exactly is going wrong here.

Any help is appreciated.

As in the comments requested here are some results of

SELECT CAST(nodename AS VARBINARY(MAX)) FROM [MyDB].[DBSpace01].t_node 

0x41004900530049004E0054002F004D004D00530049004C006900730074002F0030000000 0x41004900530049004E0054002F004D004D00530049004C006900730074002F0031000000